talos-obmc-linux/include/linux/spinlock.h, branch dev-4.13-fsi

atomics: Add header comment so spin_unlock_wait()

2017-06-08T15:25:29+00:00

There is material describing the ordering guarantees provided by spin_unlock_wait(), but it is not necessarily easy to find. This commit therefore adds a docbook header comment to this function informally describing its semantics. Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra

locking/spinlocks: Remove the unused spin_lock_bh_nested() API

2017-01-12T08:33:39+00:00

The spin_lock_bh_nested() API is defined but is not used anywhere in the kernel. So all spin_lock_bh_nested() and related APIs are now removed. Signed-off-by: Waiman Long Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1483975612-16447-1-git-send-email-longman@redhat.com Signed-off-by: Ingo Molnar

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2015-09-01T15:40:25+00:00

Pull x86 asm changes from Ingo Molnar: "The biggest changes in this cycle were: - Revamp, simplify (and in some cases fix) Time Stamp Counter (TSC) primitives. (Andy Lutomirski) - Add new, comprehensible entry and exit handlers written in C. (Andy Lutomirski) - vm86 mode cleanups and fixes. (Brian Gerst) - 32-bit compat code cleanups. (Brian Gerst) The amount of simplification in low level assembly code is already palpable: arch/x86/entry/entry_32.S | 130 +---- arch/x86/entry/entry_64.S | 197 ++----- but more simplifications are planned. There's also the usual laudry mix of low level changes - see the changelog for details" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (83 commits) x86/asm: Drop repeated macro of X86_EFLAGS_AC definition x86/asm/msr: Make wrmsrl() a function x86/asm/delay: Introduce an MWAITX-based delay with a configurable timer x86/asm: Add MONITORX/MWAITX instruction support x86/traps: Weaken context tracking entry assertions x86/asm/tsc: Add rdtscll() merge helper selftests/x86: Add syscall_nt selftest selftests/x86: Disable sigreturn_64 x86/vdso: Emit a GNU hash x86/entry: Remove do_notify_resume(), syscall_trace_leave(), and their TIF masks x86/entry/32: Migrate to C exit path x86/entry/32: Remove 32-bit syscall audit optimizations x86/vm86: Rename vm86->v86flags and v86mask x86/vm86: Rename vm86->vm86_info to user_vm86 x86/vm86: Clean up vm86.h includes x86/vm86: Move the vm86 IRQ definitions to vm86.h x86/vm86: Use the normal pt_regs area for vm86 x86/vm86: Eliminate 'struct kernel_vm86_struct' x86/vm86: Move fields from 'struct kernel_vm86_struct' to 'struct vm86' x86/vm86: Move vm86 fields out of 'thread_struct' ...

rcu,locking: Privatize smp_mb__after_unlock_lock()

2015-08-04T15:49:21+00:00

RCU is the only thing that uses smp_mb__after_unlock_lock(), and is likely the only thing that ever will use it, so this commit makes this macro private to RCU. Signed-off-by: Paul E. McKenney Cc: Will Deacon Cc: Peter Zijlstra Cc: Benjamin Herrenschmidt Cc: "linux-arch@vger.kernel.org"

locking/spinlocks: Force inlining of spinlock ops

2015-07-21T08:14:07+00:00

With both gcc 4.7.2 and 4.9.2, sometimes GCC mysteriously doesn't inline very small functions we expect to be inlined. See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122 In particular, with this config: http://busybox.net/~vda/kernel_config there are more than a thousand copies of tiny spinlock-related functions: $ nm --size-sort vmlinux | grep -iF ' t ' | uniq -c | grep -v '^ *1 ' | sort -rn | grep ' spin' 473 000000000000000b t spin_unlock_irqrestore 292 000000000000000b t spin_unlock 215 000000000000000b t spin_lock 134 000000000000000b t spin_unlock_irq 130 000000000000000b t spin_unlock_bh 120 000000000000000b t spin_lock_irq 106 000000000000000b t spin_lock_bh Disassembly: ffffffff81004720 : ffffffff81004720: 55 push %rbp ffffffff81004721: 48 89 e5 mov %rsp,%rbp ffffffff81004724: e8 f8 4e e2 02 callq <_raw_spin_lock> ffffffff81004729: 5d pop %rbp ffffffff8100472a: c3 retq This patch fixes this via s/inline/__always_inline/ in spinlock.h. This decreases vmlinux by about 40k: text data bss dec hex filename 82375570 22255544 20627456 125258570 7774b4a vmlinux.before 82335059 22255416 20627456 125217931 776ac8b vmlinux Signed-off-by: Denys Vlasenko Cc: Andrew Morton Cc: Andy Lutomirski Cc: Bart Van Assche Cc: Borislav Petkov Cc: Brian Gerst Cc: David Rientjes Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Thomas Graf Link: http://lkml.kernel.org/r/1436812263-15243-1-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar

documentation: memory-barriers: Fix smp_mb__before_spinlock() semantics

2015-05-27T19:57:27+00:00

Our current documentation claims that, when followed by an ACQUIRE, smp_mb__before_spinlock() orders prior loads against subsequent loads and stores, which isn't the intent. This commit therefore fixes the documentation to state that this sequence orders only prior stores against subsequent loads and stores. In addition, the original intent of smp_mb__before_spinlock() was to only order prior loads against subsequent stores, however, people have started using it as if it ordered prior loads against subsequent loads and stores. This commit therefore also updates smp_mb__before_spinlock()'s header comment to reflect this new reality. Cc: Oleg Nesterov Cc: "Paul E. McKenney" Cc: Peter Zijlstra Signed-off-by: Will Deacon Signed-off-by: Paul E. McKenney

spinlock: Add spin_lock_bh_nested()

2015-01-03T19:32:57+00:00

Signed-off-by: Thomas Graf Signed-off-by: David S. Miller

locking/spinlocks: Always evaluate the second argument of spin_lock_nested()

2014-08-13T08:32:38+00:00

Evaluating a macro argument only if certain configuration options have been selected is confusing and error-prone. Hence always evaluate the second argument of spin_lock_nested(). An intentional side effect of this patch is that it avoids that the following warning is reported for netif_addr_lock_nested() when building with CONFIG_DEBUG_LOCK_ALLOC=n and with W=1: include/linux/netdevice.h: In function 'netif_addr_lock_nested': include/linux/netdevice.h:2865:6: warning: variable 'subclass' set but not used [-Wunused-but-set-variable] int subclass = SINGLE_DEPTH_NESTING; ^ Signed-off-by: Bart Van Assche Signed-off-by: Peter Zijlstra Cc: David Rientjes Cc: David S. Miller Cc: Andrew Morton Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Paul E. McKenney Link: http://lkml.kernel.org/r/53E4A7F8.1040700@acm.org Signed-off-by: Ingo Molnar

locking: Add an smp_mb__after_unlock_lock() for UNLOCK+BLOCK barrier

2013-12-16T10:36:13+00:00

The Linux kernel has traditionally required that an UNLOCK+LOCK pair act as a full memory barrier when either (1) that UNLOCK+LOCK pair was executed by the same CPU or task, or (2) the same lock variable was used for the UNLOCK and LOCK. It now seems likely that very few places in the kernel rely on this full-memory-barrier semantic, and with the advent of queued locks, providing this semantic either requires complex reasoning, or for some architectures, added overhead. This commit therefore adds a smp_mb__after_unlock_lock(), which may be placed after a LOCK primitive to restore the full-memory-barrier semantic. All definitions are currently no-ops, but will be upgraded for some architectures when queued locks arrive. Signed-off-by: Paul E. McKenney Reviewed-by: Peter Zijlstra Cc: Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/r/1386799151-2219-5-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

sched: fix the theoretical signal_wake_up() vs schedule() race

2013-08-13T15:19:26+00:00

This is only theoretical, but after try_to_wake_up(p) was changed to check p->state under p->pi_lock the code like __set_current_state(TASK_INTERRUPTIBLE); schedule(); can miss a signal. This is the special case of wait-for-condition, it relies on try_to_wake_up/schedule interaction and thus it does not need mb() between __set_current_state() and if(signal_pending). However, this __set_current_state() can move into the critical section protected by rq->lock, now that try_to_wake_up() takes another lock we need to ensure that it can't be reordered with "if (signal_pending(current))" check inside that section. The patch is actually one-liner, it simply adds smp_wmb() before spin_lock_irq(rq->lock). This is what try_to_wake_up() already does by the same reason. We turn this wmb() into the new helper, smp_mb__before_spinlock(), for better documentation and to allow the architectures to change the default implementation. While at it, kill smp_mb__after_lock(), it has no callers. Perhaps we can also add smp_mb__before/after_spinunlock() for prepare_to_wait(). Signed-off-by: Oleg Nesterov Acked-by: Peter Zijlstra Signed-off-by: Linus Torvalds