linux/include
Oleg Nesterov e0acd0a68e sched: fix the theoretical signal_wake_up() vs schedule() race
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 <oleg@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-08-13 08:19:26 -07:00
..
acpi ACPI: Try harder to resolve _ADR collisions for bridges 2013-08-07 22:55:00 +02:00
asm-generic Merge branch 'cpuinit-delete' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2013-07-07 11:01:19 -07:00
clocksource
crypto
drm drm: fix 64 bit drm fixed point helpers 2013-07-30 17:24:13 -04:00
dt-bindings Pin control fixes for the v3.11 series: 2013-07-28 18:19:27 -07:00
keys
kvm ARM: KVM: Allow host virt timer irq to be different from guest timer virt irq 2013-06-26 10:50:02 -07:00
linux sched: fix the theoretical signal_wake_up() vs schedule() race 2013-08-13 08:19:26 -07:00
math-emu
media [media] v4l2: added missing mutex.h include to v4l2-ctrls.h 2013-07-26 10:14:52 -03:00
memory
misc
net net: rename CONFIG_NET_LL_RX_POLL to CONFIG_NET_RX_BUSY_POLL 2013-08-01 15:11:17 -07:00
pcmcia
ras
rdma Merge branches 'af_ib', 'cxgb4', 'misc', 'mlx5', 'ocrdma', 'qib' and 'srp' into for-next 2013-07-08 11:22:11 -07:00
rxrpc
scsi [SCSI] libiscsi: Added new boot entries in the session sysfs 2013-06-26 18:04:11 -07:00
sound ASoC: More updates for v3.11 2013-06-28 13:36:22 +02:00
target target: make queue_tm_rsp() return void 2013-07-07 18:36:53 -07:00
trace This contains fixes, optimizations and some clean ups 2013-07-22 19:07:24 -07:00
uapi Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless into for-davem 2013-08-01 14:30:59 -04:00
video Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2013-07-09 16:04:31 -07:00
xen Merge branch 'for-3.11/drivers' of git://git.kernel.dk/linux-block 2013-07-22 19:02:52 -07:00
Kbuild