]> git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/commit
ipc/sem.c: update/correct memory barriers
authorManfred Spraul <manfred@colorfullife.com>
Fri, 14 Aug 2015 22:35:10 +0000 (15:35 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 14 Aug 2015 22:56:32 +0000 (15:56 -0700)
commit3ed1f8a99d70ea1cd1508910eb107d0edcae5009
treee969912641af3d1095025d90d55dc33d9af2a10b
parent7f6bf39bbdd1dcccd103ba7dce8496a8e72e7df4
ipc/sem.c: update/correct memory barriers

sem_lock() did not properly pair memory barriers:

!spin_is_locked() and spin_unlock_wait() are both only control barriers.
The code needs an acquire barrier, otherwise the cpu might perform read
operations before the lock test.

As no primitive exists inside <include/spinlock.h> and since it seems
noone wants another primitive, the code creates a local primitive within
ipc/sem.c.

With regards to -stable:

The change of sem_wait_array() is a bugfix, the change to sem_lock() is a
nop (just a preprocessor redefinition to improve the readability).  The
bugfix is necessary for all kernels that use sem_wait_array() (i.e.:
starting from 3.10).

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Kirill Tkhai <ktkhai@parallels.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: <stable@vger.kernel.org> [3.10+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ipc/sem.c