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Manfred Spraul
3ed1f8a99d
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 <[email protected]> Reported-by: Oleg Nesterov <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: Kirill Tkhai <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Davidlohr Bueso <[email protected]> Cc: <[email protected]> [3.10+] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>