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* Merge branch 'timers-core-for-linus' of ↵Linus Torvalds2014-01-208-254/+190
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer changes from Ingo Molnar: - ARM clocksource/clockevent improvements and fixes - generic timekeeping updates: TAI fixes/improvements, cleanups - Posix cpu timer cleanups and improvements - dynticks updates: full dynticks bugfixes, optimizations and cleanups * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits) clocksource: Timer-sun5i: Switch to sched_clock_register() timekeeping: Remove comment that's mostly out of date rtc-cmos: Add an alarm disable quirk timekeeper: fix comment typo for tk_setup_internals() timekeeping: Fix missing timekeeping_update in suspend path timekeeping: Fix CLOCK_TAI timer/nanosleep delays tick/timekeeping: Call update_wall_time outside the jiffies lock timekeeping: Avoid possible deadlock from clock_was_set_delayed timekeeping: Fix potential lost pv notification of time change timekeeping: Fix lost updates to tai adjustment clocksource: sh_cmt: Add clk_prepare/unprepare support clocksource: bcm_kona_timer: Remove unused bcm_timer_ids clocksource: vt8500: Remove deprecated IRQF_DISABLED clocksource: tegra: Remove deprecated IRQF_DISABLED clocksource: misc drivers: Remove deprecated IRQF_DISABLED clocksource: sh_mtu2: Remove unnecessary platform_set_drvdata() clocksource: sh_tmu: Remove unnecessary platform_set_drvdata() clocksource: armada-370-xp: Enable timer divider only when needed clocksource: clksrc-of: Warn if no clock sources are found clocksource: orion: Switch to sched_clock_register() ...
| * Merge branch 'fortglx/3.14/time' of ↵Ingo Molnar2014-01-124-27/+29
| |\ | | | | | | | | | | | | | | | | | | | | | git://git.linaro.org/people/john.stultz/linux into timers/core Pull timekeeping updates from John Stultz. Signed-off-by: Ingo Molnar <mingo@kernel.org>
| | * timekeeping: Remove comment that's mostly out of dateJohn Stultz2013-12-231-10/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Prior to 92bb1fcf57a0c2e45f7e67fbf0a8ed475a749236 (Only do nanosecond rounding on GENERIC_TIME_VSYSCALL_OLD systems), the comment here was accuate, but now we can mostly avoid the extra rounding which causes the unlikey to be actually likely here. So remove the out of date comment. Signed-off-by: John Stultz <john.stultz@linaro.org>
| | * timekeeper: fix comment typo for tk_setup_internals()Yijing Wang2013-12-231-1/+2
| | | | | | | | | | | | | | | | | | | | | Fix trivial comment typo for tk_setup_internals(). Signed-off-by: Yijing Wang <wangyijing@huawei.com> Signed-off-by: John Stultz <john.stultz@linaro.org>
| | * timekeeping: Fix missing timekeeping_update in suspend pathJohn Stultz2013-12-231-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since 48cdc135d4840 (Implement a shadow timekeeper), we have to call timekeeping_update() after any adjustment to the timekeeping structure in order to make sure that any adjustments to the structure persist. In the timekeeping suspend path, we udpate the timekeeper structure, so we should be sure to update the shadow-timekeeper before releasing the timekeeping locks. Currently this isn't done. In most cases, the next time related code to run would be timekeeping_resume, which does update the shadow-timekeeper, but in an abundence of caution, this patch adds the call to timekeeping_update() in the suspend path. Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: stable <stable@vger.kernel.org> #3.10+ Signed-off-by: John Stultz <john.stultz@linaro.org>
| | * timekeeping: Fix CLOCK_TAI timer/nanosleep delaysJohn Stultz2013-12-231-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A think-o in the calculation of the monotonic -> tai time offset results in CLOCK_TAI timers and nanosleeps to expire late (the latency is ~2x the tai offset). Fix this by adding the tai offset from the realtime offset instead of subtracting. Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: stable <stable@vger.kernel.org> #3.10+ Signed-off-by: John Stultz <john.stultz@linaro.org>
| | * tick/timekeeping: Call update_wall_time outside the jiffies lockJohn Stultz2013-12-234-15/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since the xtime lock was split into the timekeeping lock and the jiffies lock, we no longer need to call update_wall_time() while holding the jiffies lock. Thus, this patch splits update_wall_time() out from do_timer(). This allows us to get away from calling clock_was_set_delayed() in update_wall_time() and instead use the standard clock_was_set() call that previously would deadlock, as it causes the jiffies lock to be acquired. Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: John Stultz <john.stultz@linaro.org>
| | * timekeeping: Avoid possible deadlock from clock_was_set_delayedJohn Stultz2013-12-231-2/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | As part of normal operaions, the hrtimer subsystem frequently calls into the timekeeping code, creating a locking order of hrtimer locks -> timekeeping locks clock_was_set_delayed() was suppoed to allow us to avoid deadlocks between the timekeeping the hrtimer subsystem, so that we could notify the hrtimer subsytem the time had changed while holding the timekeeping locks. This was done by scheduling delayed work that would run later once we were out of the timekeeing code. But unfortunately the lock chains are complex enoguh that in scheduling delayed work, we end up eventually trying to grab an hrtimer lock. Sasha Levin noticed this in testing when the new seqlock lockdep enablement triggered the following (somewhat abrieviated) message: [ 251.100221] ====================================================== [ 251.100221] [ INFO: possible circular locking dependency detected ] [ 251.100221] 3.13.0-rc2-next-20131206-sasha-00005-g8be2375-dirty #4053 Not tainted [ 251.101967] ------------------------------------------------------- [ 251.101967] kworker/10:1/4506 is trying to acquire lock: [ 251.101967] (timekeeper_seq){----..}, at: [<ffffffff81160e96>] retrigger_next_event+0x56/0x70 [ 251.101967] [ 251.101967] but task is already holding lock: [ 251.101967] (hrtimer_bases.lock#11){-.-...}, at: [<ffffffff81160e7c>] retrigger_next_event+0x3c/0x70 [ 251.101967] [ 251.101967] which lock already depends on the new lock. [ 251.101967] [ 251.101967] [ 251.101967] the existing dependency chain (in reverse order) is: [ 251.101967] -> #5 (hrtimer_bases.lock#11){-.-...}: [snipped] -> #4 (&rt_b->rt_runtime_lock){-.-...}: [snipped] -> #3 (&rq->lock){-.-.-.}: [snipped] -> #2 (&p->pi_lock){-.-.-.}: [snipped] -> #1 (&(&pool->lock)->rlock){-.-...}: [ 251.101967] [<ffffffff81194803>] validate_chain+0x6c3/0x7b0 [ 251.101967] [<ffffffff81194d9d>] __lock_acquire+0x4ad/0x580 [ 251.101967] [<ffffffff81194ff2>] lock_acquire+0x182/0x1d0 [ 251.101967] [<ffffffff84398500>] _raw_spin_lock+0x40/0x80 [ 251.101967] [<ffffffff81153e69>] __queue_work+0x1a9/0x3f0 [ 251.101967] [<ffffffff81154168>] queue_work_on+0x98/0x120 [ 251.101967] [<ffffffff81161351>] clock_was_set_delayed+0x21/0x30 [ 251.101967] [<ffffffff811c4bd1>] do_adjtimex+0x111/0x160 [ 251.101967] [<ffffffff811e2711>] compat_sys_adjtimex+0x41/0x70 [ 251.101967] [<ffffffff843a4b49>] ia32_sysret+0x0/0x5 [ 251.101967] -> #0 (timekeeper_seq){----..}: [snipped] [ 251.101967] other info that might help us debug this: [ 251.101967] [ 251.101967] Chain exists of: timekeeper_seq --> &rt_b->rt_runtime_lock --> hrtimer_bases.lock#11 [ 251.101967] Possible unsafe locking scenario: [ 251.101967] [ 251.101967] CPU0 CPU1 [ 251.101967] ---- ---- [ 251.101967] lock(hrtimer_bases.lock#11); [ 251.101967] lock(&rt_b->rt_runtime_lock); [ 251.101967] lock(hrtimer_bases.lock#11); [ 251.101967] lock(timekeeper_seq); [ 251.101967] [ 251.101967] *** DEADLOCK *** [ 251.101967] [ 251.101967] 3 locks held by kworker/10:1/4506: [ 251.101967] #0: (events){.+.+.+}, at: [<ffffffff81154960>] process_one_work+0x200/0x530 [ 251.101967] #1: (hrtimer_work){+.+...}, at: [<ffffffff81154960>] process_one_work+0x200/0x530 [ 251.101967] #2: (hrtimer_bases.lock#11){-.-...}, at: [<ffffffff81160e7c>] retrigger_next_event+0x3c/0x70 [ 251.101967] [ 251.101967] stack backtrace: [ 251.101967] CPU: 10 PID: 4506 Comm: kworker/10:1 Not tainted 3.13.0-rc2-next-20131206-sasha-00005-g8be2375-dirty #4053 [ 251.101967] Workqueue: events clock_was_set_work So the best solution is to avoid calling clock_was_set_delayed() while holding the timekeeping lock, and instead using a flag variable to decide if we should call clock_was_set() once we've released the locks. This works for the case here, where the do_adjtimex() was the deadlock trigger point. Unfortuantely, in update_wall_time() we still hold the jiffies lock, which would deadlock with the ipi triggered by clock_was_set(), preventing us from calling it even after we drop the timekeeping lock. So instead call clock_was_set_delayed() at that point. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: stable <stable@vger.kernel.org> #3.10+ Reported-by: Sasha Levin <sasha.levin@oracle.com> Tested-by: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: John Stultz <john.stultz@linaro.org>
| | * timekeeping: Fix potential lost pv notification of time changeJohn Stultz2013-12-231-9/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In 780427f0e11 (Indicate that clock was set in the pvclock gtod notifier), logic was added to pass a CLOCK_WAS_SET notification to the pvclock notifier chain. While that patch added a action flag returned from accumulate_nsecs_to_secs(), it only uses the returned value in one location, and not in the logarithmic accumulation. This means if a leap second triggered during the logarithmic accumulation (which is most likely where it would happen), the notification that the clock was set would not make it to the pv notifiers. This patch extends the logarithmic_accumulation pass down that action flag so proper notification will occur. This patch also changes the varialbe action -> clock_set per Ingo's suggestion. Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: <xen-devel@lists.xen.org> Cc: stable <stable@vger.kernel.org> #3.11+ Signed-off-by: John Stultz <john.stultz@linaro.org>
| | * timekeeping: Fix lost updates to tai adjustmentJohn Stultz2013-12-231-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since 48cdc135d4840 (Implement a shadow timekeeper), we have to call timekeeping_update() after any adjustment to the timekeeping structure in order to make sure that any adjustments to the structure persist. Unfortunately, the updates to the tai offset via adjtimex do not trigger this update, causing adjustments to the tai offset to be made and then over-written by the previous value at the next update_wall_time() call. This patch resovles the issue by calling timekeeping_update() right after setting the tai offset. Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: stable <stable@vger.kernel.org> #3.10+ Signed-off-by: John Stultz <john.stultz@linaro.org>
| * | Merge branch 'linus' into timers/coreIngo Molnar2014-01-1226-170/+226
| |\ \ | | |/ | |/| | | | | | | | | | Pick up the latest fixes and refresh the branch. Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | posix-timers: Convert abuses of BUG_ON to WARN_ONFrederic Weisbecker2013-12-091-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The posix cpu timers code makes a heavy use of BUG_ON() but none of these concern fatal issues that require to stop the machine. So let's just warn the user when some internal state slips out of our hands. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Remove remaining uses of tasklist_lockFrederic Weisbecker2013-12-091-32/+44
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The remaining uses of tasklist_lock were mostly about synchronizing against sighand modifications, getting coherent and safe group samples and also thread/process wide timers list handling. All of this is already safely synchronizable with the target's sighand lock. Let's use it on these places instead. Also update the comments about locking. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Use sighand lock instead of tasklist_lock on timer deletionFrederic Weisbecker2013-12-091-6/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Timer deletion doesn't need the tasklist lock. We need to protect against: * concurrent access to the lists p->cputime_expires and p->sighand->cputime_expires * task reaping that may also delete the timer list entry * timer firing We already hold the timer lock which protects us against concurrent timer firing. The rest only need the targets sighand to be locked. So hold it and drop the use of tasklist_lock there. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Use sighand lock instead of tasklist_lock for task clock sampleFrederic Weisbecker2013-12-091-3/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There is no need for the tasklist_lock just to take a process wide clock sample. All we need is to get a coherent sample that doesn't race with exit() and exec(): * exit() may be concurrently reaping a task and flushing its time * sighand is unstable under exit() and exec(), and the latter also result in group leader that can change To protect against these, locking the target's sighand is enough. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Consolidate posix_cpu_clock_get()Frederic Weisbecker2013-12-091-34/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Consolidate the clock sampling common code used for both local and remote targets. Note that this introduces a tiny user ABI change: if a PID is passed to clock_gettime() along the clockid, we used to forbid a process wide clock sample when that PID doesn't belong to a group leader. Now after this patch we allow process wide clock samples if that PID belongs to the current task, even if the current task is not the group leader. But local process wide clock samples are allowed if PID == 0 (current task) even if the current task is not the group leader. So in the end this should be no big deal as this actually harmonize the behaviour when the remote sample is actually a local one. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Remove useless clock sample on timers cleanupFrederic Weisbecker2013-12-091-23/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | a0b2062b0904ef07944c4a6e4d0f88ee44f1e9f2 ("posix_timers: fix racy timer delta caching on task exit") forgot to remove the arguments used for timer caching. Fix this leftover. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Remove dead task special caseFrederic Weisbecker2013-12-091-45/+25
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now that we've removed all the optimizations that could result in NULL timer's targets, we can remove all the associated special case handling. Also add some warnings on NULL targets to spot any possible leftover. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Cleanup reaped target handlingFrederic Weisbecker2013-12-091-6/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When a timer's target is seen to be buried, for example on calls to timer_gettime(), the posix cpu timers code behaves a bit like a garbage collector and releases early the reference to the task. Then again, this optimization complicates the code for no much value: it's up to the user to release the timer and its associated ressources by calling timer_delete() after it buries the target tasks. Remove this to simplify the code. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Remove dead process posix cpu timers cachingFrederic Weisbecker2013-12-091-34/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now that we removed dead thread posix cpu timers caching, lets remove the dead process wide version. This caching is similar to the per thread version but it should be even more rare: * If the process id dead, we are not reading its timers status from a thread belonging to its group since they are all dead. So this caching only concern remote process timers reads. Now posix cpu timers using itimers or timer_settime() can't do remote process timers anyway so it's not even clear if there is actually a user for this caching. * Unlike per thread timers caching, this only applies to zombies targets. Buried targets' process wide timers return 0 values. But then again, timer_gettime() can't read remote process timers, so if the process is dead, there can't be any reader left anyway. Then again this caching seem to complicate the code for corner cases that are probably not worth it. So lets get rid of it. Also remove the sample snapshot on dying process timer that is now useless, as suggested by Kosaki. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | posix-timers: Remove dead thread posix cpu timers cachingFrederic Weisbecker2013-12-091-18/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When a task is exiting or has exited, its posix cpu timers don't tick anymore and won't elapse further. It's too late for them to expire. So any further call to timer_gettime() on these timers will return the same remaining expiry time. The current code optimize this by caching the remaining delta and storing it where we use to save the absolute expiration time. This way, the future calls to timer_gettime() won't need to compute the difference between the absolute expiration time and the current time anymore. Now this optimization doesn't seem to bring much value. Computing the timer remaining delta is not very costly. Fetching the timer value OTOH can be costly in two ways: * CPUCLOCK_SCHED read requires to lock the target's rq. But some optimizations are on the way to make task_sched_runtime() not holding the rq lock of a non-running target. * CPUCLOCK_VIRT/CPUCLOCK_PROF read simply consist in fetching current->utime/current->stime except when the system uses full dynticks cputime accounting. The latter requires a per task lock in order to correctly compute user and system time. But once the target is dead, this lock shouldn't be contended anyway. All in one this caching doesn't seem to be justified. Given that it complicates the code significantly for few wins, let's remove it on single thread timers. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
| * | Merge branch 'timers/core-v2' of ↵Ingo Molnar2013-12-046-47/+35
| |\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/core Pull dynticks updates from Frederic Weisbecker: * Fix a bug where posix cpu timers requeued due to interval got ignored on full dynticks CPUs (not a regression though as it only impacts full dynticks and the bug is there since we merged full dynticks). * Optimizations and cleanups on the use of per CPU APIs to improve code readability, performance and debuggability in the nohz subsystem; * Optimize posix cpu timer by sparing stub workqueue queue with full dynticks off case * Rename some functions to extend with *_this_cpu() suffix for clarity * Refine the naming of some context tracking subsystem state accessors * Trivial spelling fix by Paul Gortmaker Signed-off-by: Ingo Molnar <mingo@kernel.org>
| | * | posix-timers: Fix full dynticks CPUs kick on timer reschedulingFrederic Weisbecker2013-12-021-11/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A posix CPU timer can be rearmed while it is firing or after it is notified with a signal. This can happen for example with timers that were set with a non zero interval in timer_settime(). This rearming can happen in two places: 1) On timer firing time, which happens on the target's tick. If the timer can't trigger a signal because it is ignored, it reschedules itself to honour the timer interval. 2) On signal handling from the timer's notification target. This one can be a different task than the timer's target itself. Once the signal is notified, the notification target rearms the timer, again to honour the timer interval. When a timer is rearmed, we need to notify the full dynticks CPUs such that they restart their tick in case they are running tasks that may have a share in elapsing this timer. Now the 1st case above handles full dynticks CPUs with a call to posix_cpu_timer_kick_nohz() from the posix cpu timer firing code. But the second case ignores the fact that some CPUs may run non-idle tasks with their tick off. As a result, when a timer is resheduled after its signal notification, the full dynticks CPUs may completely ignore it and not tick on the timer as expected This patch fixes this bug by handling both cases in one. All we need is to move the kick to the rearming common code in posix_cpu_timer_schedule(). Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Olivier Langlois <olivier@olivierlanglois.net>
| | * | posix-timers: Spare workqueue if there is no full dynticks CPU to kickFrederic Weisbecker2013-12-021-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | After a posix cpu timer is set, a workqueue is scheduled in order to kick the full dynticks CPUs and let them restart their tick if necessary in case the task they are running is concerned by the new timer. This kick is implemented by way of IPIs, which require interrupts to be enabled, hence the need for a workqueue to raise them because the posix cpu timer set path has interrupts disabled. Now if there is no full dynticks CPU on the system, the workqueue is still scheduled but it simply won't send any IPI and return immediately. So lets spare that worqueue when it is not needed. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org>
| | * | context_tracking: Wrap static key check into more intuitive function nameFrederic Weisbecker2013-12-021-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Use a function with a meaningful name to check the global context tracking state. static_key_false() is a bit confusing for reviewers. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org>
| | * | nohz: Convert a few places to use local per cpu accessesFrederic Weisbecker2013-12-024-31/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A few functions use remote per CPU access APIs when they deal with local values. Just do the right conversion to improve performance, code readability and debug checks. While at it, lets extend some of these function names with *_this_cpu() suffix in order to display their purpose more clearly. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org>
* | | | Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2014-01-2024-323/+3087
|\ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler changes from Ingo Molnar: - Add the initial implementation of SCHED_DEADLINE support: a real-time scheduling policy where tasks that meet their deadlines and periodically execute their instances in less than their runtime quota see real-time scheduling and won't miss any of their deadlines. Tasks that go over their quota get delayed (Available to privileged users for now) - Clean up and fix preempt_enable_no_resched() abuse all around the tree - Do sched_clock() performance optimizations on x86 and elsewhere - Fix and improve auto-NUMA balancing - Fix and clean up the idle loop - Apply various cleanups and fixes * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits) sched: Fix __sched_setscheduler() nice test sched: Move SCHED_RESET_ON_FORK into attr::sched_flags sched: Fix up attr::sched_priority warning sched: Fix up scheduler syscall LTP fails sched: Preserve the nice level over sched_setscheduler() and sched_setparam() calls sched/core: Fix htmldocs warnings sched/deadline: No need to check p if dl_se is valid sched/deadline: Remove unused variables sched/deadline: Fix sparse static warnings m68k: Fix build warning in mac_via.h sched, thermal: Clean up preempt_enable_no_resched() abuse sched, net: Fixup busy_loop_us_clock() sched, net: Clean up preempt_enable_no_resched() abuse sched/preempt: Fix up missed PREEMPT_NEED_RESCHED folding sched/preempt, locking: Rework local_bh_{dis,en}able() sched/clock, x86: Avoid a runtime condition in native_sched_clock() sched/clock: Fix up clear_sched_clock_stable() sched/clock, x86: Use a static_key for sched_clock_stable sched/clock: Remove local_irq_disable() from the clocks sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs ...
| * | | | sched: Fix __sched_setscheduler() nice testPeter Zijlstra2014-01-161-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the introduction of sched_attr::sched_nice we need to check if we've got permission to actually change the nice value. Daniel found that can_nice() would always fail; and upon inspection it turns out that can_nice() only tests to see if we can lower the nice value, but it doesn't validate if we're lowering or not. Therefore amend the test to only call can_nice() when we lower the nice value. Reported-and-Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: raistlin@linux.it Cc: juri.lelli@gmail.com Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Fixes: d50dde5a10f3 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI") Link: http://lkml.kernel.org/r/20140116165425.GA9481@laptop.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Move SCHED_RESET_ON_FORK into attr::sched_flagsPeter Zijlstra2014-01-161-14/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I noticed the new sched_{set,get}attr() calls didn't properly deal with the SCHED_RESET_ON_FORK hack. Instead of propagating the flags in high bits nonsense use the brand spanking new attr::sched_flags field. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Dario Faggioli <raistlin@linux.it> Link: http://lkml.kernel.org/r/20140115162242.GJ31570@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Fix up attr::sched_priority warningPeter Zijlstra2014-01-161-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fengguang Wu reported the following build warning: > kernel/sched/core.c:3067 __sched_setscheduler() warn: unsigned 'attr->sched_priority' is never less than zero. Since it doesn't make sense for attr::sched_priority to be negative, remove the check, since we already test for an upper limit any actual negative values passed in through the old param::sched_priority field will still be detected. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Dario Faggioli <raistlin@linux.it> Fixes: d50dde5a10f3 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI") Link: http://lkml.kernel.org/n/tip-fid9nalzii2r5voxtf4eh5kz@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Fix up scheduler syscall LTP failsPeter Zijlstra2014-01-161-3/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Wu reported LTP failures: > ltp.sched_setparam02.1.TFAIL > ltp.sched_setparam02.2.TFAIL > ltp.sched_setparam02.3.TFAIL > ltp.sched_setparam03.1.TFAIL There were 2 things wrong; firstly __setscheduler() failed on sched_setparam()'s policy = -1, fix that by reading from p->policy in that case. Secondly, getparam() (and getattr()) would still report !0 sched_priority for !FIFO/RR tasks after having been such. So unconditionally set p->rt_priority. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Dario Faggioli <raistlin@linux.it> Fixes: d50dde5a10f3 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI") Link: http://lkml.kernel.org/r/20140115153320.GH31570@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Preserve the nice level over sched_setscheduler() and ↵Peter Zijlstra2014-01-161-2/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | sched_setparam() calls Previously sched_setscheduler() and sched_setparam() would not affect the nice value of a task, restore this behaviour. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: raistlin@linux.it Cc: juri.lelli@gmail.com Cc: Michael wang <wangyun@linux.vnet.ibm.com> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Fixes: d50dde5a10f3 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI") Link: http://lkml.kernel.org/r/20140115113015.GB31570@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/core: Fix htmldocs warningsJuri Lelli2014-01-161-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fengguang Wu's kbuild test robot reported the following new htmldocs warnings: >>> Warning(kernel/sched/core.c:3380): No description found for parameter 'uattr' >>> Warning(kernel/sched/core.c:3380): Excess function parameter 'attr' description in 'sys_sched_setattr' >>> Warning(kernel/sched/core.c:3520): No description found for parameter 'uattr' >>> Warning(kernel/sched/core.c:3520): Excess function parameter 'attr' description in 'sys_sched_getattr' The second argument to sys_sched_{setattr,getattr}() is named uattr (not attr). Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Juri Lelli <juri.lelli@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Dario Faggioli <raistlin@linux.it> Fixes: d50dde5a10f3 ("sched: Add new scheduler syscalls to support an extended scheduling parameters ABI") Link: http://lkml.kernel.org/r/52D5552D.5000102@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/deadline: No need to check p if dl_se is validJuri Lelli2014-01-161-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Dan Carpenter reported new 'Smatch' warnings: > tree: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core > head: 130816ce4d5f69167324f7272e70aa3d641677c6 > commit: 1baca4ce16b8cc7d4f50be1f7914799af30a2861 [17/50] sched/deadline: Add SCHED_DEADLINE SMP-related data structures & logic > > kernel/sched/deadline.c:937 pick_next_task_dl() warn: variable dereferenced before check 'p' (see line 934) BUG_ON() already fires if pick_next_dl_entity() doesn't return a valid dl_se. No need to check if p is valid afterward. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Juri Lelli <juri.lelli@gmail.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Fixes: 1baca4ce16b8 ("sched/deadline: Add SCHED_DEADLINE SMP-related data structures & logic") Link: http://lkml.kernel.org/r/52D54E25.6060100@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/deadline: Remove unused variablesPeter Zijlstra2014-01-161-11/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | fix these new sparse warnings: >> kernel/sched/core.c:305:14: sparse: symbol 'sysctl_sched_dl_period' was not declared. Should it be static? >> kernel/sched/core.c:306:5: sparse: symbol 'sysctl_sched_dl_runtime' was not declared. Should it be static? Better still, they're completely unused so remove them. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Link: http://lkml.kernel.org/n/tip-ke0shkG7vMnzmcdqhhiymyem@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/deadline: Fix sparse static warningsFengguang Wu2014-01-161-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | new sparse warnings: >> kernel/sched/cpudeadline.c:38:6: sparse: symbol 'cpudl_exchange' was not declared. Should it be static? >> kernel/sched/cpudeadline.c:46:6: sparse: symbol 'cpudl_heapify' was not declared. Should it be static? >> kernel/sched/cpudeadline.c:71:6: sparse: symbol 'cpudl_change_key' was not declared. Should it be static? >> kernel/sched/cpudeadline.c:195:15: sparse: memset with byte count of 163928 Signed-off-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Fixes: 6bfd6d72f51c ("sched/deadline: speed up SCHED_DEADLINE pushes with a push-heap") Link: http://lkml.kernel.org/r/52d47f8c.EYJsA5+mELPBk4t6\%fengguang.wu@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/preempt: Fix up missed PREEMPT_NEED_RESCHED foldingPeter Zijlstra2014-01-132-9/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With various drivers wanting to inject idle time; we get people calling idle routines outside of the idle loop proper. Therefore we need to be extra careful about not missing TIF_NEED_RESCHED -> PREEMPT_NEED_RESCHED propagations. While looking at this, I also realized there's a small window in the existing idle loop where we can miss TIF_NEED_RESCHED; when it hits right after the tif_need_resched() test at the end of the loop but right before the need_resched() test at the start of the loop. So move preempt_fold_need_resched() out of the loop where we're guaranteed to have TIF_NEED_RESCHED set. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-x9jgh45oeayzajz2mjt0y7d6@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/preempt, locking: Rework local_bh_{dis,en}able()Peter Zijlstra2014-01-131-29/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently local_bh_disable() is out-of-line for no apparent reason. So inline it to save a few cycles on call/return nonsense, the function body is a single add on x86 (a few loads and store extra on load/store archs). Also expose two new local_bh functions: __local_bh_{dis,en}able_ip(unsigned long ip, unsigned int cnt); Which implement the actual local_bh_{dis,en}able() behaviour. The next patch uses the exposed @cnt argument to optimize bh lock functions. With build fixes from Jacob Pan. Cc: rjw@rjwysocki.net Cc: rui.zhang@intel.com Cc: jacob.jun.pan@linux.intel.com Cc: Mike Galbraith <bitbucket@online.de> Cc: hpa@zytor.com Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: lenb@kernel.org Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/clock: Fix up clear_sched_clock_stable()Peter Zijlstra2014-01-131-1/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The below tells us the static_key conversion has a problem; since the exact point of clearing that flag isn't too important, delay the flip and use a workqueue to process it. [ ] TSC synchronization [CPU#0 -> CPU#22]: [ ] Measured 8 cycles TSC warp between CPUs, turning off TSC clock. [ ] [ ] ====================================================== [ ] [ INFO: possible circular locking dependency detected ] [ ] 3.13.0-rc3-01745-g848b0d0322cb-dirty #637 Not tainted [ ] ------------------------------------------------------- [ ] swapper/0/1 is trying to acquire lock: [ ] (jump_label_mutex){+.+...}, at: [<ffffffff8115a637>] jump_label_lock+0x17/0x20 [ ] [ ] but task is already holding lock: [ ] (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff8109408b>] cpu_hotplug_begin+0x2b/0x60 [ ] [ ] which lock already depends on the new lock. [ ] [ ] [ ] the existing dependency chain (in reverse order) is: [ ] [ ] -> #1 (cpu_hotplug.lock){+.+.+.}: [ ] [<ffffffff810def00>] lock_acquire+0x90/0x130 [ ] [<ffffffff81661f83>] mutex_lock_nested+0x63/0x3e0 [ ] [<ffffffff81093fdc>] get_online_cpus+0x3c/0x60 [ ] [<ffffffff8104cc67>] arch_jump_label_transform+0x37/0x130 [ ] [<ffffffff8115a3cf>] __jump_label_update+0x5f/0x80 [ ] [<ffffffff8115a48d>] jump_label_update+0x9d/0xb0 [ ] [<ffffffff8115aa6d>] static_key_slow_inc+0x9d/0xb0 [ ] [<ffffffff810c0f65>] sched_feat_set+0xf5/0x100 [ ] [<ffffffff810c5bdc>] set_numabalancing_state+0x2c/0x30 [ ] [<ffffffff81d12f3d>] numa_policy_init+0x1af/0x1b7 [ ] [<ffffffff81cebdf4>] start_kernel+0x35d/0x41f [ ] [<ffffffff81ceb5a5>] x86_64_start_reservations+0x2a/0x2c [ ] [<ffffffff81ceb6a2>] x86_64_start_kernel+0xfb/0xfe [ ] [ ] -> #0 (jump_label_mutex){+.+...}: [ ] [<ffffffff810de141>] __lock_acquire+0x1701/0x1eb0 [ ] [<ffffffff810def00>] lock_acquire+0x90/0x130 [ ] [<ffffffff81661f83>] mutex_lock_nested+0x63/0x3e0 [ ] [<ffffffff8115a637>] jump_label_lock+0x17/0x20 [ ] [<ffffffff8115aa3b>] static_key_slow_inc+0x6b/0xb0 [ ] [<ffffffff810ca775>] clear_sched_clock_stable+0x15/0x20 [ ] [<ffffffff810503b3>] mark_tsc_unstable+0x23/0x70 [ ] [<ffffffff810772cb>] check_tsc_sync_source+0x14b/0x150 [ ] [<ffffffff81076612>] native_cpu_up+0x3a2/0x890 [ ] [<ffffffff810941cb>] _cpu_up+0xdb/0x160 [ ] [<ffffffff810942c9>] cpu_up+0x79/0x90 [ ] [<ffffffff81d0af6b>] smp_init+0x60/0x8c [ ] [<ffffffff81cebf42>] kernel_init_freeable+0x8c/0x197 [ ] [<ffffffff8164e32e>] kernel_init+0xe/0x130 [ ] [<ffffffff8166beec>] ret_from_fork+0x7c/0xb0 [ ] [ ] other info that might help us debug this: [ ] [ ] Possible unsafe locking scenario: [ ] [ ] CPU0 CPU1 [ ] ---- ---- [ ] lock(cpu_hotplug.lock); [ ] lock(jump_label_mutex); [ ] lock(cpu_hotplug.lock); [ ] lock(jump_label_mutex); [ ] [ ] *** DEADLOCK *** [ ] [ ] 2 locks held by swapper/0/1: [ ] #0: (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff81094037>] cpu_maps_update_begin+0x17/0x20 [ ] #1: (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff8109408b>] cpu_hotplug_begin+0x2b/0x60 [ ] [ ] stack backtrace: [ ] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc3-01745-g848b0d0322cb-dirty #637 [ ] Hardware name: Supermicro X8DTN/X8DTN, BIOS 4.6.3 01/08/2010 [ ] ffffffff82c9c270 ffff880236843bb8 ffffffff8165c5f5 ffffffff82c9c270 [ ] ffff880236843bf8 ffffffff81658c02 ffff880236843c80 ffff8802368586a0 [ ] ffff880236858678 0000000000000001 0000000000000002 ffff880236858000 [ ] Call Trace: [ ] [<ffffffff8165c5f5>] dump_stack+0x4e/0x7a [ ] [<ffffffff81658c02>] print_circular_bug+0x1f9/0x207 [ ] [<ffffffff810de141>] __lock_acquire+0x1701/0x1eb0 [ ] [<ffffffff816680ff>] ? __atomic_notifier_call_chain+0x8f/0xb0 [ ] [<ffffffff810def00>] lock_acquire+0x90/0x130 [ ] [<ffffffff8115a637>] ? jump_label_lock+0x17/0x20 [ ] [<ffffffff8115a637>] ? jump_label_lock+0x17/0x20 [ ] [<ffffffff81661f83>] mutex_lock_nested+0x63/0x3e0 [ ] [<ffffffff8115a637>] ? jump_label_lock+0x17/0x20 [ ] [<ffffffff8115a637>] jump_label_lock+0x17/0x20 [ ] [<ffffffff8115aa3b>] static_key_slow_inc+0x6b/0xb0 [ ] [<ffffffff810ca775>] clear_sched_clock_stable+0x15/0x20 [ ] [<ffffffff810503b3>] mark_tsc_unstable+0x23/0x70 [ ] [<ffffffff810772cb>] check_tsc_sync_source+0x14b/0x150 [ ] [<ffffffff81076612>] native_cpu_up+0x3a2/0x890 [ ] [<ffffffff810941cb>] _cpu_up+0xdb/0x160 [ ] [<ffffffff810942c9>] cpu_up+0x79/0x90 [ ] [<ffffffff81d0af6b>] smp_init+0x60/0x8c [ ] [<ffffffff81cebf42>] kernel_init_freeable+0x8c/0x197 [ ] [<ffffffff8164e320>] ? rest_init+0xd0/0xd0 [ ] [<ffffffff8164e32e>] kernel_init+0xe/0x130 [ ] [<ffffffff8166beec>] ret_from_fork+0x7c/0xb0 [ ] [<ffffffff8164e320>] ? rest_init+0xd0/0xd0 [ ] ------------[ cut here ]------------ [ ] WARNING: CPU: 0 PID: 1 at /usr/src/linux-2.6/kernel/smp.c:374 smp_call_function_many+0xad/0x300() [ ] Modules linked in: [ ] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc3-01745-g848b0d0322cb-dirty #637 [ ] Hardware name: Supermicro X8DTN/X8DTN, BIOS 4.6.3 01/08/2010 [ ] 0000000000000009 ffff880236843be0 ffffffff8165c5f5 0000000000000000 [ ] ffff880236843c18 ffffffff81093d8c 0000000000000000 0000000000000000 [ ] ffffffff81ccd1a0 ffffffff810ca951 0000000000000000 ffff880236843c28 [ ] Call Trace: [ ] [<ffffffff8165c5f5>] dump_stack+0x4e/0x7a [ ] [<ffffffff81093d8c>] warn_slowpath_common+0x8c/0xc0 [ ] [<ffffffff810ca951>] ? sched_clock_tick+0x1/0xa0 [ ] [<ffffffff81093dda>] warn_slowpath_null+0x1a/0x20 [ ] [<ffffffff8110b72d>] smp_call_function_many+0xad/0x300 [ ] [<ffffffff8104f200>] ? arch_unregister_cpu+0x30/0x30 [ ] [<ffffffff8104f200>] ? arch_unregister_cpu+0x30/0x30 [ ] [<ffffffff810ca951>] ? sched_clock_tick+0x1/0xa0 [ ] [<ffffffff8110ba96>] smp_call_function+0x46/0x80 [ ] [<ffffffff8104f200>] ? arch_unregister_cpu+0x30/0x30 [ ] [<ffffffff8110bb3c>] on_each_cpu+0x3c/0xa0 [ ] [<ffffffff810ca950>] ? sched_clock_idle_sleep_event+0x20/0x20 [ ] [<ffffffff810ca951>] ? sched_clock_tick+0x1/0xa0 [ ] [<ffffffff8104f964>] text_poke_bp+0x64/0xd0 [ ] [<ffffffff810ca950>] ? sched_clock_idle_sleep_event+0x20/0x20 [ ] [<ffffffff8104ccde>] arch_jump_label_transform+0xae/0x130 [ ] [<ffffffff8115a3cf>] __jump_label_update+0x5f/0x80 [ ] [<ffffffff8115a48d>] jump_label_update+0x9d/0xb0 [ ] [<ffffffff8115aa6d>] static_key_slow_inc+0x9d/0xb0 [ ] [<ffffffff810ca775>] clear_sched_clock_stable+0x15/0x20 [ ] [<ffffffff810503b3>] mark_tsc_unstable+0x23/0x70 [ ] [<ffffffff810772cb>] check_tsc_sync_source+0x14b/0x150 [ ] [<ffffffff81076612>] native_cpu_up+0x3a2/0x890 [ ] [<ffffffff810941cb>] _cpu_up+0xdb/0x160 [ ] [<ffffffff810942c9>] cpu_up+0x79/0x90 [ ] [<ffffffff81d0af6b>] smp_init+0x60/0x8c [ ] [<ffffffff81cebf42>] kernel_init_freeable+0x8c/0x197 [ ] [<ffffffff8164e320>] ? rest_init+0xd0/0xd0 [ ] [<ffffffff8164e32e>] kernel_init+0xe/0x130 [ ] [<ffffffff8166beec>] ret_from_fork+0x7c/0xb0 [ ] [<ffffffff8164e320>] ? rest_init+0xd0/0xd0 [ ] ---[ end trace 6ff1df5620c49d26 ]--- [ ] tsc: Marking TSC unstable due to check_tsc_sync_source failed Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-v55fgqj3nnyqnngmvuu8ep6h@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/clock, x86: Use a static_key for sched_clock_stablePeter Zijlstra2014-01-134-10/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order to avoid the runtime condition and variable load turn sched_clock_stable into a static_key. Also provide a shorter implementation of local_clock() and cpu_clock(int) when sched_clock_stable==1. MAINLINE PRE POST sched_clock_stable: 1 1 1 (cold) sched_clock: 329841 221876 215295 (cold) local_clock: 301773 234692 220773 (warm) sched_clock: 38375 25602 25659 (warm) local_clock: 100371 33265 27242 (warm) rdtsc: 27340 24214 24208 sched_clock_stable: 0 0 0 (cold) sched_clock: 382634 235941 237019 (cold) local_clock: 396890 297017 294819 (warm) sched_clock: 38194 25233 25609 (warm) local_clock: 143452 71234 71232 (warm) rdtsc: 27345 24245 24243 Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/n/tip-eummbdechzz37mwmpags1gjr@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched/clock: Remove local_irq_disable() from the clocksPeter Zijlstra2014-01-131-28/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now that x86 no longer requires IRQs disabled for sched_clock() and ia64 never had this requirement (it doesn't seem to do cpufreq at all), we can remove the requirement of disabling IRQs. MAINLINE PRE POST sched_clock_stable: 1 1 1 (cold) sched_clock: 329841 257223 221876 (cold) local_clock: 301773 309889 234692 (warm) sched_clock: 38375 25280 25602 (warm) local_clock: 100371 85268 33265 (warm) rdtsc: 27340 24247 24214 sched_clock_stable: 0 0 0 (cold) sched_clock: 382634 301224 235941 (cold) local_clock: 396890 399870 297017 (warm) sched_clock: 38194 25630 25233 (warm) local_clock: 143452 129629 71234 (warm) rdtsc: 27345 24307 24245 Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/n/tip-36e5kohiasnr106d077mgubp@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | locking: Optimize lock_bh functionsPeter Zijlstra2014-01-131-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently all _bh_ lock functions do two preempt_count operations: local_bh_disable(); preempt_disable(); and for the unlock: preempt_enable_no_resched(); local_bh_enable(); Since its a waste of perfectly good cycles to modify the same variable twice when you can do it in one go; use the new __local_bh_{dis,en}able_ip() functions that allow us to provide a preempt_count value to add/sub. So define SOFTIRQ_LOCK_OFFSET as the offset a _bh_ lock needs to add/sub to be done in one go. As a bonus it gets rid of the preempt_enable_no_resched() usage. This reduces a 1000 loops of: spin_lock_bh(&bh_lock); spin_unlock_bh(&bh_lock); from 53596 cycles to 51995 cycles. I didn't do enough measurements to say for absolute sure that the result is significant but the the few runs I did for each suggest it is so. Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: jacob.jun.pan@linux.intel.com Cc: Mike Galbraith <bitbucket@online.de> Cc: hpa@zytor.com Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: lenb@kernel.org Cc: rjw@rjwysocki.net Cc: rui.zhang@intel.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Factor out the on_null_domain() checks in trigger_load_balance()Daniel Lezcano2014-01-131-3/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The test on_null_domain is done twice in the trigger_load_balance function. Move the test at the begin of the function, so there is only one check. Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-9-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Pass 'struct rq' to nohz_idle_balance()Daniel Lezcano2014-01-131-6/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cpu information is stored in the struct rq. Pass the struct rq to nohz_idle_balance, so all the functions called in run_rebalance_domains have the same parameters and the 'this_cpu' variable becomes pointless. Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> [ Added !SMP build fix. ] Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-8-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Pass 'struct rq' to rebalance_domains()Daniel Lezcano2014-01-131-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cpu information is stored in the struct rq and the caller of the rebalance_domains function pass the cpu to retrieve the struct rq but it already has the struct rq info. Replace the cpu parameter with the struct rq. Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-7-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Remove unused parameter from nohz_balancer_kick()Daniel Lezcano2014-01-131-4/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cpu parameter is no longer needed in nohz_balancer_kick, let's remove the parameter. Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-6-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Remove unused parameter from find_new_ilb()Daniel Lezcano2014-01-131-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The 'call_cpu' is never used in the function. Remove it. Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-5-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Pass 'struct rq' to on_null_domain()Daniel Lezcano2014-01-131-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The on_null_domain() function is getting the cpu to retrieve the struct rq associated with it. Pass 'struct rq' directly to the function as the caller already has the info. Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-4-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Reduce nohz_kick_needed() parametersDaniel Lezcano2014-01-131-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cpu information is already stored in the struct rq, so no need to pass it as parameter to the nohz_kick_needed function. The caller of this function just called idle_cpu() before to fill the rq->idle_balance field. Use rq->cpu and rq->idle_balance. Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-3-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | sched: Reduce trigger_load_balance() parametersDaniel Lezcano2014-01-133-3/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cpu information is already stored in the struct rq, so no need to pass it as parameter to the trigger_load_balance function. Cc: linaro-kernel@lists.linaro.org Cc: preeti.lkml@gmail.com Cc: mingo@redhat.com Cc: peterz@infradead.org Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1389008085-9069-2-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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