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Date: Mon, 10 Aug 2015 10:15:52 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Manfred Spraul <manfred@...orfullife.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, 1vier1@....de, Oleg Nesterov <oleg@...hat.com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Kirill Tkhai <ktkhai@...allels.com>, Ingo Molnar <mingo@...hat.com>, Josh Poimboeuf <jpoimboe@...hat.com>, stable@...r.kernel.org Subject: Re: [PATCH] ipc/sem.c: Update/correct memory barriers On Sun, Aug 09, 2015 at 07:55:39PM +0200, Manfred Spraul wrote: > 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). > > Andrew: Could you include it into your tree and forward it? > > Signed-off-by: Manfred Spraul <manfred@...orfullife.com> > Reported-by: Oleg Nesterov <oleg@...hat.com> > Cc: <stable@...r.kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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