On 02/28/2013 06:09 PM, Linus Torvalds wrote:
So I almost think that *everything* there in the semaphore code could be done under RCU. The actual spinlock doesn't seem to much matter, at least for semaphores. The semaphore values themselves seem to be protected by the atomic operations, but I might be wrong about that, I didn't even check.
Checking try_atomic_semop and do_smart_update, it looks like neither is using atomic operations. That part of the semaphore code would still benefit from spinlocks. The way the code handles a whole batch of semops all at once, potentially to multiple semaphores at once, and with the ability to undo all of the operations, it looks like the spinlock will still need to be per block of semaphores. I guess the code may still benefit from Michel's locking code, after the permission stuff has been moved from under the spinlock. Two remaining worries are the security_sem_free call and the non-RCU list_del calls from freeary, called from the SEM_RMID code. They are probably fine, but worth another pair of eyes... -- All rights reversed -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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