• Manfred Spraul's avatar
    ipc/sem.c: update/correct memory barriers · 3ed1f8a9
    Manfred Spraul authored
    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
    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: default avatarManfred Spraul <manfred@colorfullife.com>
    Reported-by: default avatarOleg Nesterov <oleg@redhat.com>
    Acked-by: default avatarPeter 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: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
sem.c 56.1 KB