kernel.git/arch/x86/include/asm/spinlock.h, branch linux-3.10.y

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

2014-01-09T20:24:23Z

commit e0acd0a68ec7dbf6b7a81a87a867ebd7ac9b76c4 upstream. 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 Signed-off-by: Greg Kroah-Hartman

x86/spinlocks: Fix comment in spinlock.h

2012-08-22T07:52:47Z

This comment is no longer true. We support up to 2^16 CPUs because __ticket_t is an u16 if NR_CPUS is larger than 256. Signed-off-by: Richard Weinberger Signed-off-by: Andrew Morton Signed-off-by: Ingo Molnar

x86: spinlock.h: Remove REG_PTR_MODE

2012-03-30T17:01:59Z

REG_PTR_MODE has no users at all. Signed-off-by: Richard Weinberger Link: http://lkml.kernel.org/r/1333064283-3109-1-git-send-email-richard@nod.at Acked-by: Acked-by: Jan Beulich Signed-off-by: H. Peter Anvin

x86/spinlocks: Eliminate TICKET_MASK

2012-02-07T09:09:54Z

The definition of it being questionable already (unnecessarily including a cast), and it being used in a single place that can be written shorter without it, remove this #define. Along the same lines, simplify __ticket_spin_is_locked()'s main expression, which was the more convoluted way because of needs that went away with the recent type changes by Jeremy. This is pure cleanup, no functional change intended. Signed-off-by: Jan Beulich Acked-by: Jeremy Fitzhardinge Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/4F2C06020200007800071066@nat28.tlf.novell.com Signed-off-by: Ingo Molnar

x86/cmpxchg: add a locked add() helper

2011-11-25T18:42:59Z

Mostly to remove some conditional code in spinlock.h. Signed-off-by: Jeremy Fitzhardinge

x86, ticketlock: remove obsolete comment

2011-09-28T06:37:20Z

The note about partial registers is not really relevent now that we rely on gcc to generate all the assembler. Signed-off-by: Jeremy Fitzhardinge

x86, ticketlock: Make __ticket_spin_trylock common

2011-08-29T20:46:34Z

Make trylock code common regardless of ticket size. (Also, rename arch_spinlock.slock to head_tail.) Signed-off-by: Jeremy Fitzhardinge Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org Signed-off-by: H. Peter Anvin

x86, ticketlock: Convert __ticket_spin_lock to use xadd()

2011-08-29T20:46:07Z

Convert the two variants of __ticket_spin_lock() to use xadd(), which has the effect of making them identical, so remove the duplicate function. Signed-off-by: Jeremy Fitzhardinge Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org Signed-off-by: H. Peter Anvin

x86, ticketlock: Convert spin loop to C

2011-08-29T20:45:43Z

The inner loop of __ticket_spin_lock isn't doing anything very special, so reimplement it in C. For the 8 bit ticket lock variant, we use a register union to get direct access to the lower and upper bytes in the tickets, but unfortunately gcc won't generate a direct comparison between the two halves of the register, so the generated asm isn't quite as pretty as the hand-coded version. However benchmarking shows that this is actually a small improvement in runtime performance on some benchmarks, and never a slowdown. We also need to make sure there's a barrier at the end of the lock loop to make sure that the compiler doesn't move any instructions from within the locked region into the region where we don't yet own the lock. Signed-off-by: Jeremy Fitzhardinge Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org Signed-off-by: H. Peter Anvin

x86, ticketlock: Clean up types and accessors

2011-08-29T20:45:19Z

A few cleanups to the way spinlocks are defined and accessed: - define __ticket_t which is the size of a spinlock ticket (ie, enough bits to hold all the cpus) - Define struct arch_spinlock as a union containing plain slock and the head and tail tickets - Use head and tail to implement some of the spinlock predicates. - Make all ticket variables unsigned. - Use TICKET_SHIFT to form constants Most of this will be used in later patches. Signed-off-by: Jeremy Fitzhardinge Link: http://lkml.kernel.org/r/4E5BCC40.3030501@goop.org Signed-off-by: H. Peter Anvin