summaryrefslogtreecommitdiffstats
path: root/drivers/tty/tty_ldisc.c
Commit message (Collapse)AuthorAgeFilesLines
* tty: Convert termios_mutex to termios_rwsemPeter Hurley2013-07-231-5/+5
| | | | | | | | | termios is commonly accessed unsafely (especially by N_TTY) because the existing mutex forces exclusive access. Convert existing usage. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Don't change receive_room for ioctl(TIOCSETD)Peter Hurley2013-07-231-3/+0
| | | | | | | | | tty_set_ldisc() is guaranteed exclusive use of the line discipline by tty_ldisc_lock_pair_timeout(); shutting off input by resetting receive_room is unnecessary. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Clarify multiple-references comment in TIOCSETD ioctlPeter Hurley2013-07-231-4/+6
| | | | | Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Fix hangup race with TIOCSETD ioctlPeter Hurley2013-07-231-4/+2
| | | | | | | The hangup may already have happened; check for that state also. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Clarify ldisc variablePeter Hurley2013-07-231-7/+7
| | | | | | | | Rename o_ldisc to avoid confusion with the ldisc of the 'other' tty. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Replace ldisc locking with ldisc_semPeter Hurley2013-07-231-283/+46
| | | | | | | | | | | | | | | | | | | | | | Line discipline locking was performed with a combination of a mutex, a status bit, a count, and a waitqueue -- basically, a rw semaphore. Replace the existing combination with an ld_semaphore. Fixes: 1) the 'reference acquire after ldisc locked' bug 2) the over-complicated halt mechanism 3) lock order wrt. tty_lock() 4) dropping locks while changing ldisc 5) previously unidentified deadlock while locking ldisc from both linked ttys concurrently 6) previously unidentified recursive deadlocks Adds much-needed lockdep diagnostics. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Add lock/unlock ldisc pair functionsPeter Hurley2013-07-231-0/+87
| | | | | | | | | Just as the tty pair must be locked in a stable sequence (ie, independent of which is consider the 'other' tty), so must the ldisc pair be locked in a stable sequence as well. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Fix tty_ldisc_lock name collisionPeter Hurley2013-07-231-23/+23
| | | | | | | | The file scope spinlock identifier, tty_ldisc_lock, will collide with the file scope lock function tty_ldisc_lock() so rename it. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Remove redundant tty_wait_until_sent()Peter Hurley2013-03-181-9/+0
| | | | | | | tty_ioctl() already waits until sent. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Locate get/put ldisc functions togetherPeter Hurley2013-03-181-23/+23
| | | | | Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Fold one-line assign function into callersPeter Hurley2013-03-181-25/+6
| | | | | | | | Now that tty_ldisc_assign() is a one-line file-scoped function, remove it and perform the simple assignment at its call sites. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Document unsafe ldisc reference acquirePeter Hurley2013-03-181-9/+5
| | | | | | | | | | | | | | | | | | | | | | | | Merge get_ldisc() into its only call site. Note how, after merging, the unsafe acquire of an ldisc reference is obvious. CPU 0 in tty_ldisc_try() | CPU 1 in tty_ldisc_halt() | test_bit(TTY_LDISC, &tty_flags) | if (true) | clear_bit(TTY_LDISC, &tty_flags) tty->ldisc != 0? | atomic_read(&tty->ldisc->users) if (true) | ret_val == 1? atomic_inc(&tty->ldisc->users) | if (false) | wait | <goes on assuming safe ldisc use> | <doesn't wait - proceeds w/ close> | The spin lock in tty_ldisc_try() does nothing wrt synchronizing the ldisc halt since it's not acquired as part of halting. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Separate release semantics of ldisc referencePeter Hurley2013-03-181-34/+35
| | | | | | | | | | | | | | | tty_ldisc_ref()/tty_ldisc_unref() have usage semantics equivalent to down_read_trylock()/up_read(). Only callers of tty_ldisc_put() are performing the additional operations necessary for proper ldisc teardown, and then only after ensuring no outstanding 'read lock' remains. Thus, tty_ldisc_unref() should never be the last reference; WARN if it is. Conversely, tty_ldisc_put() should never be destructing if the use count != 1. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Add ldisc hangup debug messagesPeter Hurley2013-03-181-0/+19
| | | | | | | | | | | | | | | | | | | | Expected typical debug log: [ 582.721965] tty_open: opening pts3... [ 582.721970] tty_open: opening pts3... [ 582.721977] tty_release: pts3 (tty count=3)... [ 582.721980] tty_release: ptm3 (tty count=1)... [ 582.722015] pts3 vhangup... [ 582.722020] tty_ldisc_hangup: pts3: closing ldisc: ffff88007a920540 [ 582.724128] tty_release: pts3 (tty count=2)... [ 582.724217] tty_ldisc_hangup: pts3: re-opened ldisc: ffff88007a920580 [ 582.724221] tty_release: ptm3: final close [ 582.724234] tty_ldisc_release: ptm3: closing ldisc: ffff88007a920a80 [ 582.724238] tty_ldisc_release: ptm3: ldisc closed [ 582.724241] tty_release: ptm3: freeing structure... [ 582.724741] tty_open: opening pts3... Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Fix 'deferred reopen' ldisc commentPeter Hurley2013-03-181-4/+5
| | | | | | | | This comment is a victim of code migration from "tty: Fix the ldisc hangup race"; re-parent it. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Make core responsible for synchronizing its workPeter Hurley2013-03-181-20/+4
| | | | | | | | | The tty core relies on the ldisc layer for synchronizing destruction of the tty. Instead, the final tty release must wait for any pending tty work to complete prior to tty destruction. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Complete ownership transfer of flip buffersPeter Hurley2013-03-181-35/+12
| | | | | | | | | | | | | | | | | Waiting for buffer work to complete is not required for safely performing changes to the line discipline, once the line discipline is halted. The buffer work routine, flush_to_ldisc(), will be unable to acquire an ldisc ref and all existing references were waited until released (so it can't already have one). Ensure running buffer work which may reference the soon-to-be-gone tty completes and any buffer work running after this point retrieves a NULL tty. Also, ensure all buffer work is cancelled on port destruction. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Don't reenable already enabled ldiscPeter Hurley2013-03-181-1/+1
| | | | | | | | | tty_ldisc_hangup() guarantees the ldisc is enabled (or that there is no ldisc). Since __tty_hangup() was the only user, re-define tty_ldisc_enable() in file-scope. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Wait for SAK work before waiting for hangup workPeter Hurley2013-03-181-1/+1
| | | | | | | | SAK work may schedule hangup work (if TTY_SOFT_SAK is defined), thus SAK work must be flushed before hangup work. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Halt both ldiscs concurrentlyPeter Hurley2013-03-181-13/+25
| | | | | | | | | | | | | | | The pty driver does not obtain an ldisc reference to the linked tty when writing. When the ldiscs are sequentially halted, it is possible for one ldisc to be halted, and before the second ldisc can be halted, a concurrent write schedules buffer work on the first ldisc. This can lead to an access-after-free error when the scheduled buffer work starts on the closed ldisc. Prevent subsequent use after halt by performing each stage of the halt on both ttys. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Strengthen no-subsequent-use guarantee of tty_ldisc_halt()Peter Hurley2013-03-181-18/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In preparation for destructing and freeing the tty, the line discipline must first be brought to an inactive state before it can be destructed. This line discipline shutdown must: - disallow new users of the ldisc - wait for existing ldisc users to finish - only then, cancel/flush their pending/running work Factor tty_ldisc_wait_idle() from tty_set_ldisc() and tty_ldisc_kill() to ensure this shutdown order. Failure to provide this guarantee can result in scheduled work running after the tty has already been freed, as indicated in the following log message: [ 88.331234] WARNING: at drivers/tty/tty_buffer.c:435 flush_to_ldisc+0x194/0x1d0() [ 88.334505] Hardware name: Bochs [ 88.335618] tty is bad=-1 [ 88.335703] Modules linked in: netconsole configfs bnep rfcomm bluetooth ...... [ 88.345272] Pid: 39, comm: kworker/1:1 Tainted: G W 3.7.0-next-20121129+ttydebug-xeon #20121129+ttydebug [ 88.347736] Call Trace: [ 88.349024] [<ffffffff81058aff>] warn_slowpath_common+0x7f/0xc0 [ 88.350383] [<ffffffff81058bf6>] warn_slowpath_fmt+0x46/0x50 [ 88.351745] [<ffffffff81432bd4>] flush_to_ldisc+0x194/0x1d0 [ 88.353047] [<ffffffff816f7fe1>] ? _raw_spin_unlock_irq+0x21/0x50 [ 88.354190] [<ffffffff8108a809>] ? finish_task_switch+0x49/0xe0 [ 88.355436] [<ffffffff81077ad1>] process_one_work+0x121/0x490 [ 88.357674] [<ffffffff81432a40>] ? __tty_buffer_flush+0x90/0x90 [ 88.358954] [<ffffffff81078c84>] worker_thread+0x164/0x3e0 [ 88.360247] [<ffffffff81078b20>] ? manage_workers+0x120/0x120 [ 88.361282] [<ffffffff8107e230>] kthread+0xc0/0xd0 [ 88.362284] [<ffffffff816f0000>] ? cmos_do_probe+0x2eb/0x3bf [ 88.363391] [<ffffffff8107e170>] ? flush_kthread_worker+0xb0/0xb0 [ 88.364797] [<ffffffff816fff6c>] ret_from_fork+0x7c/0xb0 [ 88.366087] [<ffffffff8107e170>] ? flush_kthread_worker+0xb0/0xb0 [ 88.367266] ---[ end trace 453a7c9f38fbfec0 ]--- Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Relocate tty_ldisc_halt() to avoid forward declarationPeter Hurley2013-03-181-23/+23
| | | | | | | | tty_ldisc_halt() will use the file-scoped function, tty_ldisc_wait_idle(), in the following patch. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Fix ldisc halt sequence on hangupPeter Hurley2013-03-181-20/+19
| | | | | | | | | | | Flip buffer work cannot be cancelled until all outstanding ldisc references have been released. Convert the ldisc ref wait into a full ldisc halt with buffer work cancellation. Note that the legacy mutex is not held while cancelling. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Remove unnecessary re-test of ldisc ref countPeter Hurley2013-03-181-19/+19
| | | | | | | | | | | | | | Since the tty->ldisc is prevented from being changed by tty_set_ldisc() when a tty is being hung up, re-testing the ldisc user count is unnecessary -- ie, it cannot be a different ldisc and the user count cannot have increased (assuming the caller meets the precondition that TTY_LDISC flag is cleared) Removal of the 'early-out' locking optimization is necessary for the subsequent patch 'tty: Fix ldisc halt sequence on hangup'. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Refactor wait for ldisc refs out of tty_ldisc_hangup()Peter Hurley2013-03-181-18/+36
| | | | | | | | | Refactor tty_ldisc_hangup() to extract standalone function, tty_ldisc_hangup_wait_idle(), to wait for ldisc references to be released. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Add diagnostic for halted line disciplinePeter Hurley2013-03-181-1/+6
| | | | | | | | | | Flip buffer work must not be scheduled by the line discipline after the line discipline has been halted; issue warning. Note: drivers can still schedule flip buffer work. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: don't deadlock while flushing workqueueSebastian Andrzej Siewior2013-01-151-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since commit 89c8d91e31f2 ("tty: localise the lock") I see a dead lock in one of my dummy_hcd + g_nokia test cases. The first run was usually okay, the second often resulted in a splat by lockdep and the third was usually a dead lock. Lockdep complained about tty->hangup_work and tty->legacy_mutex taken both ways: | ====================================================== | [ INFO: possible circular locking dependency detected ] | 3.7.0-rc6+ #204 Not tainted | ------------------------------------------------------- | kworker/2:1/35 is trying to acquire lock: | (&tty->legacy_mutex){+.+.+.}, at: [<c14051e6>] tty_lock_nested+0x36/0x80 | | but task is already holding lock: | ((&tty->hangup_work)){+.+...}, at: [<c104f6e4>] process_one_work+0x124/0x5e0 | | which lock already depends on the new lock. | | the existing dependency chain (in reverse order) is: | | -> #2 ((&tty->hangup_work)){+.+...}: | [<c107fe74>] lock_acquire+0x84/0x190 | [<c104d82d>] flush_work+0x3d/0x240 | [<c12e6986>] tty_ldisc_flush_works+0x16/0x30 | [<c12e7861>] tty_ldisc_release+0x21/0x70 | [<c12e0dfc>] tty_release+0x35c/0x470 | [<c1105e28>] __fput+0xd8/0x270 | [<c1105fcd>] ____fput+0xd/0x10 | [<c1051dd9>] task_work_run+0xb9/0xf0 | [<c1002a51>] do_notify_resume+0x51/0x80 | [<c140550a>] work_notifysig+0x35/0x3b | | -> #1 (&tty->legacy_mutex/1){+.+...}: | [<c107fe74>] lock_acquire+0x84/0x190 | [<c140276c>] mutex_lock_nested+0x6c/0x2f0 | [<c14051e6>] tty_lock_nested+0x36/0x80 | [<c1405279>] tty_lock_pair+0x29/0x70 | [<c12e0bb8>] tty_release+0x118/0x470 | [<c1105e28>] __fput+0xd8/0x270 | [<c1105fcd>] ____fput+0xd/0x10 | [<c1051dd9>] task_work_run+0xb9/0xf0 | [<c1002a51>] do_notify_resume+0x51/0x80 | [<c140550a>] work_notifysig+0x35/0x3b | | -> #0 (&tty->legacy_mutex){+.+.+.}: | [<c107f3c9>] __lock_acquire+0x1189/0x16a0 | [<c107fe74>] lock_acquire+0x84/0x190 | [<c140276c>] mutex_lock_nested+0x6c/0x2f0 | [<c14051e6>] tty_lock_nested+0x36/0x80 | [<c140523f>] tty_lock+0xf/0x20 | [<c12df8e4>] __tty_hangup+0x54/0x410 | [<c12dfcb2>] do_tty_hangup+0x12/0x20 | [<c104f763>] process_one_work+0x1a3/0x5e0 | [<c104fec9>] worker_thread+0x119/0x3a0 | [<c1055084>] kthread+0x94/0xa0 | [<c140ca37>] ret_from_kernel_thread+0x1b/0x28 | |other info that might help us debug this: | |Chain exists of: | &tty->legacy_mutex --> &tty->legacy_mutex/1 --> (&tty->hangup_work) | | Possible unsafe locking scenario: | | CPU0 CPU1 | ---- ---- | lock((&tty->hangup_work)); | lock(&tty->legacy_mutex/1); | lock((&tty->hangup_work)); | lock(&tty->legacy_mutex); | | *** DEADLOCK *** Before the path mentioned tty_ldisc_release() look like this: | tty_ldisc_halt(tty); | tty_ldisc_flush_works(tty); | tty_lock(); As it can be seen, it first flushes the workqueue and then grabs the tty_lock. Now we grab the lock first: | tty_lock_pair(tty, o_tty); | tty_ldisc_halt(tty); | tty_ldisc_flush_works(tty); so lockdep's complaint seems valid. The earlier version of this patch took the ldisc_mutex since the other user of tty_ldisc_flush_works() (tty_set_ldisc()) did this. Peter Hurley then said that it is should not be requried. Since it wasn't done earlier, I dropped this part. The code under tty_ldisc_kill() was executed earlier with the tty lock taken so it is taken again. I was able to reproduce the deadlock on v3.8-rc1, this patch fixes the problem in my testcase. I didn't notice any problems so far. Cc: Alan Cox <alan@linux.intel.com> Cc: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Only wakeup the line discipline idle queue when queue is activeIvo Sieben2013-01-151-1/+3
| | | | | | | | | | Before waking up the tty line discipline idle queue first check if the queue is active (non empty). This prevents unnecessary entering the critical section in the wake_up() function and therefore avoid needless scheduling overhead on a PREEMPT_RT system caused by two processes being in the same critical section. Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Use raw spin lock to protect TTY ldisc administrationIvo Sieben2012-10-241-16/+16
| | | | | | | | | | | | The global "normal" spin lock that guards the line discipline administration is replaced by a raw spin lock. On a PREEMPT_RT system this prevents unwanted scheduling overhead around the line discipline administration. On a 200 MHz AT91SAM9261 processor setup this fixes about 100us of scheduling overhead on a TTY read or write call. Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* TTY: move tty buffers to tty_portJiri Slaby2012-10-221-5/+5
| | | | | | | | | | | | | | | | | | | So this is it. The big step why we did all the work over the past kernel releases. Now everything is prepared, so nothing protects us from doing that big step. | | \ \ nnnn/^l | | | | \ / / | | | '-,.__ => \/ ,-` => | '-,.__ | O __.´´) ( .` | O __.´´) ~~~ ~~ `` ~~~ ~~ The buffers are now in the tty_port structure and we can start teaching the buffer helpers (insert char/string, flip etc.) to use tty_port instead of tty_struct all around. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Acked-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* TTY: ldisc, wait for idle ldisc in releaseJiri Slaby2012-10-221-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We reintroduced tty_ldisc_wait_idle in 100eeae2c5c (TTY: restore tty_ldisc_wait_idle) and used in set_ldisc. Then we added it also to the hangup path in 92f6fa09bd453 (TTY: ldisc, do not close until there are readers). And we noted that there is one more path: ~ Before 65b770468e98 tty_ldisc_wait_idle was called also from ~ tty_ldisc_release. It is called from tty_release, so I don't think ~ we need to restore that one. Well, I was wrong. There might still be holders of an ldisc reference. Not from userspace, but drivers. If they take a reference and a user closes the device immediately after that, we have a problem. ldisc is halted and closed by TTY, but the driver still may call some ldisc's operation and cause a crash. So restore the tty_ldisc_wait_idle call also to the third location where it was before 65b770468e98 (tty-ldisc: turn ldisc user count into a proper refcount). Now we should be safe with respect to the ldisc reference counting as all* tty_ldisc_close paths are safely called with reference count of one. * Not the one in tty_ldisc_setup's fail path. But that is called before the first open finishes. So userspace does not see it yet. Even thought the driver is given the TTY already via ->install, it should not take a reference to the ldisc yet. If some driver is to do this, we should put one tty_ldisc_wait_idle also in the setup. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Acked-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* Merge branch 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wqLinus Torvalds2012-10-021-3/+3
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull workqueue changes from Tejun Heo: "This is workqueue updates for v3.7-rc1. A lot of activities this round including considerable API and behavior cleanups. * delayed_work combines a timer and a work item. The handling of the timer part has always been a bit clunky leading to confusing cancelation API with weird corner-case behaviors. delayed_work is updated to use new IRQ safe timer and cancelation now works as expected. * Another deficiency of delayed_work was lack of the counterpart of mod_timer() which led to cancel+queue combinations or open-coded timer+work usages. mod_delayed_work[_on]() are added. These two delayed_work changes make delayed_work provide interface and behave like timer which is executed with process context. * A work item could be executed concurrently on multiple CPUs, which is rather unintuitive and made flush_work() behavior confusing and half-broken under certain circumstances. This problem doesn't exist for non-reentrant workqueues. While non-reentrancy check isn't free, the overhead is incurred only when a work item bounces across different CPUs and even in simulated pathological scenario the overhead isn't too high. All workqueues are made non-reentrant. This removes the distinction between flush_[delayed_]work() and flush_[delayed_]_work_sync(). The former is now as strong as the latter and the specified work item is guaranteed to have finished execution of any previous queueing on return. * In addition to the various bug fixes, Lai redid and simplified CPU hotplug handling significantly. * Joonsoo introduced system_highpri_wq and used it during CPU hotplug. There are two merge commits - one to pull in IRQ safe timer from tip/timers/core and the other to pull in CPU hotplug fixes from wq/for-3.6-fixes as Lai's hotplug restructuring depended on them." Fixed a number of trivial conflicts, but the more interesting conflicts were silent ones where the deprecated interfaces had been used by new code in the merge window, and thus didn't cause any real data conflicts. Tejun pointed out a few of them, I fixed a couple more. * 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (46 commits) workqueue: remove spurious WARN_ON_ONCE(in_irq()) from try_to_grab_pending() workqueue: use cwq_set_max_active() helper for workqueue_set_max_active() workqueue: introduce cwq_set_max_active() helper for thaw_workqueues() workqueue: remove @delayed from cwq_dec_nr_in_flight() workqueue: fix possible stall on try_to_grab_pending() of a delayed work item workqueue: use hotcpu_notifier() for workqueue_cpu_down_callback() workqueue: use __cpuinit instead of __devinit for cpu callbacks workqueue: rename manager_mutex to assoc_mutex workqueue: WORKER_REBIND is no longer necessary for idle rebinding workqueue: WORKER_REBIND is no longer necessary for busy rebinding workqueue: reimplement idle worker rebinding workqueue: deprecate __cancel_delayed_work() workqueue: reimplement cancel_delayed_work() using try_to_grab_pending() workqueue: use mod_delayed_work() instead of __cancel + queue workqueue: use irqsafe timer for delayed_work workqueue: clean up delayed_work initializers and add missing one workqueue: make deferrable delayed_work initializer names consistent workqueue: cosmetic whitespace updates for macro definitions workqueue: deprecate system_nrt[_freezable]_wq workqueue: deprecate flush[_delayed]_work_sync() ...
| * workqueue: deprecate flush[_delayed]_work_sync()Tejun Heo2012-08-201-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | flush[_delayed]_work_sync() are now spurious. Mark them deprecated and convert all users to flush[_delayed]_work(). If you're cc'd and wondering what's going on: Now all workqueues are non-reentrant and the regular flushes guarantee that the work item is not pending or running on any CPU on return, so there's no reason to use the sync flushes at all and they're going away. This patch doesn't make any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Ian Campbell <ian.campbell@citrix.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Mattia Dongili <malattia@linux.it> Cc: Kent Yoder <key@linux.vnet.ibm.com> Cc: David Airlie <airlied@linux.ie> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Karsten Keil <isdn@linux-pingi.de> Cc: Bryan Wu <bryan.wu@canonical.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Alasdair Kergon <agk@redhat.com> Cc: Mauro Carvalho Chehab <mchehab@infradead.org> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Cc: David Woodhouse <dwmw2@infradead.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: linux-wireless@vger.kernel.org Cc: Anton Vorontsov <cbou@mail.ru> Cc: Sangbeom Kim <sbkim73@samsung.com> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Eric Van Hensbergen <ericvh@gmail.com> Cc: Takashi Iwai <tiwai@suse.de> Cc: Steven Whitehouse <swhiteho@redhat.com> Cc: Petr Vandrovec <petr@vandrovec.name> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Avi Kivity <avi@redhat.com>
| * tty ldisc: Close/Reopen race prevention should check the proper flagShachar Shemesh2012-07-261-1/+1
| | | | | | | | | | | | | | | | | | | | | | Commit acfa747b introduced the TTY_HUPPING flag to distinguish closed TTY from currently closing ones. The test in tty_set_ldisc still remained pointing at the old flag. This causes pppd to sometimes lapse into uninterruptible sleep when killed and restarted. Signed-off-by: Shachar Shemesh <shachar@liveu.tv> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | tty: localise the lockAlan Cox2012-08-101-30/+39
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The termios and other changes mean the other protections needed on the driver tty arrays should be adequate. Turn it all back on. This contains pieces folded in from the fixes made to the original patches | From: Geert Uytterhoeven <geert@linux-m68k.org> (fix m68k) | From: Paul Gortmaker <paul.gortmaker@windriver.com> (fix cris) | From: Jiri Kosina <jkosina@suze.cz> (lockdep) | From: Eric Dumazet <eric.dumazet@gmail.com> (lockdep) Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | tty: Fix race in tty releaseAlan Cox2012-07-271-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Ian Abbott found that the tty layer would explode with the right set of parallel open and close operations. This is because we race in the handling of tty->drivers->termios[]. Correct this by Making tty_ldisc_release behave like nromal code (takes the lock, does stuff, drops the lock) Drop the tty lock earlier in tty_ldisc_release Taking the tty mutex around the driver->termios update in all cases Adding a WARN_ON to catch future screwups. I also forgot to clean up the pty resources properly. With a pty pair we need to pull both halves out of the tables. Signed-off-by: Alan Cox <alan@linux.intel.com> Tested-by: Ian Abbott <abbotti@mev.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | tty: move the termios object into the ttyAlan Cox2012-07-161-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | This will let us sort out a whole pile of tty related races. The alternative would be to keep points and refcount the termios objects. However 1. They are tiny anyway 2. Many devices don't use the stored copies 3. We can remove a pty special case Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | tty: revert incorrectly applied lock patchAlan Cox2012-07-161-38/+29
| | | | | | | | | | | | | | | | | | | | I sent GregKH this after the pre-requisites. He dropped the pre-requesites for good reason and unfortunately then applied this patch. Without this reverted you get random kernel memory corruption which will make bisecting anything between it and the properly applied patches a complete sod. Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | tty ldisc: Close/Reopen race prevention should check the proper flagShachar Shemesh2012-07-121-1/+1
| | | | | | | | | | | | | | | | | | | | | | Commit acfa747b introduced the TTY_HUPPING flag to distinguish closed TTY from currently closing ones. The test in tty_set_ldisc still remained pointing at the old flag. This causes pppd to sometimes lapse into uninterruptible sleep when killed and restarted. Signed-off-by: Shachar Shemesh <shachar@liveu.tv> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | tty: localise the lockAlan Cox2012-07-061-29/+38
|/ | | | | | | | | | | | | | | The termios and other changes mean the other protections needed on the driver tty arrays should be adequate. Turn it all back on. This contains pieces folded in from the fixes made to the original patches | From: Geert Uytterhoeven <geert@linux-m68k.org> (fix m68k) | From: Paul Gortmaker <paul.gortmaker@windriver.com> (fix cris) | From: Jiri Kosina <jkosina@suze.cz> (lockdep) | From: Eric Dumazet <eric.dumazet@gmail.com> (lockdep) Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty: Revert the tty locking series, it needs more workLinus Torvalds2012-06-021-38/+29
| | | | | | | | | | | | | | | | | | | | | | This reverts the tty layer change to use per-tty locking, because it's not correct yet, and fixing it will require some more deep surgery. The main revert is d29f3ef39be4 ("tty_lock: Localise the lock"), but there are several smaller commits that built upon it, they also get reverted here. The list of reverted commits is: fde86d310886 - tty: add lockdep annotations 8f6576ad476b - tty: fix ldisc lock inversion trace d3ca8b64b97e - pty: Fix lock inversion b1d679afd766 - tty: drop the pty lock during hangup abcefe5fc357 - tty/amiserial: Add missing argument for tty_unlock() fd11b42e3598 - cris: fix missing tty arg in wait_event_interruptible_tty call d29f3ef39be4 - tty_lock: Localise the lock The revert had a trivial conflict in the 68360serial.c staging driver that got removed in the meantime. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* tty: fix ldisc lock inversion traceAlan Cox2012-05-291-16/+25
| | | | | | | | | | | | | This is caused by tty_release using tty_lock_pair to lock both sides of the pty/tty pair, and then tty_ldisc_release dropping and relocking one side only. We can drop both fine, so drop both to avoid any lock ordering concerns. Rework the release path to fix the new locking model. Signed-off-by: Alan Cox <alan@linux.intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* tty: move global ldisc idle waitqueue to the individual ldiscIvo Sieben2012-05-101-3/+4
| | | | | | | | | | | The global wait_queue that is used for line discipline idle handling is moved to a separate wait_queue for each line instance. This prevents unnecessary blocking on one line, because of idle handling on another line. Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com> Acked-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* tty_lock: Localise the lockAlan Cox2012-05-041-15/+15
| | | | | | | | | | | | In each remaining case the tty_lock is associated with a specific tty. This means we can now lock on a per tty basis. We do need tty_lock_pair() for the pty case. Uglier but still a step in the right direction. [fixed up calls in 3 missing drivers - gregkh] Signed-off-by: Alan Cox <alan@linux.intel.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* Merge 3.2-rc3 into tty-next to handle merge conflict in tty_ldisc.cGreg Kroah-Hartman2011-11-261-7/+23
|\ | | | | | | Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| * TTY: ldisc, wait for ldisc infinitely in hangupJiri Slaby2011-11-171-2/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For /dev/console case, we do not kill all ldisc users. It's due to redirected_tty_write test in __tty_hangup. In that case there still might be a process waiting e.g. in n_tty_read for input. We wait for such processes to disappear. The problem is that we use a timeout. After this timeout, we continue closing the ldisc and start freeing tty resources. It obviously leads to crashes when the other process is woken. So to fix this, we wait infinitely before reiniting the ldisc. (The tiocsetd remains untouched -- times out after 5s.) This is nicely reproducible with this run from shell: exec 0<>/dev/console 1<>/dev/console 2<>/dev/console and stopping a getty like: systemctl stop serial-getty@ttyS0.service The crash proper may be produced only under load or with constified timing the same as for 92f6fa09b. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Dave Young <hidave.darkstar@gmail.com> Cc: Dave Jones <davej@redhat.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Dmitriy Matrosov <sgf.dma@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| * TTY: ldisc, move wait idle to callerJiri Slaby2011-11-171-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It is the only place where reinit is called from. And we really need to wait for the old ldisc to go once. Actually this is the place where the waiting originally was (before removed and re-added later). This will make the fix in the following patch easier to implement. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Dave Young <hidave.darkstar@gmail.com> Cc: Dave Jones <davej@redhat.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Dmitriy Matrosov <sgf.dma@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| * TTY: ldisc, allow waiting for ldisc arbitrarily longJiri Slaby2011-11-171-5/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To fix a nasty bug in ldisc hup vs. reinit we need to wait infinitely long for ldisc to be gone. So here we add a parameter to tty_ldisc_wait_idle to allow that. This is only a preparation for the real fix which is done in the following patches. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Dave Young <hidave.darkstar@gmail.com> Cc: Dave Jones <davej@redhat.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Dmitriy Matrosov <sgf.dma@gmail.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* | TTY: ldisc, remove some unneeded includesJiri Slaby2011-11-171-19/+1
| | | | | | | | | | | | | | | | | | They were cut&pasted from tty_io. Many of them are not needed in tty_ldisc. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* | tty_ldisc: remove unnecessary negative return check for wait_event_timeoutDave Young2011-11-151-2/+0
|/ | | | | | | | | wait_event_timeout always return value >= 0 remove the unnecessary ret < 0 check Signed-off-by: Dave Young <dyoung@redhat.com> Acked-by: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
OpenPOWER on IntegriCloud