On 05/25/2013 11:16 AM, Manfred Spraul wrote:
The double coward solution: - wakeup stays FIFO - fast switch back to per-semaphore spinlock modeThe patch a) fixes a lockup due to a missing restart. b) makes the wakeups again FIFO (as linux <= 3.0.9) c) tries to limit the time while in global lock mode as much as possible. (same as linux-3.0.10-rc1) Changes: - the wait-for-zero operations are moved into seperate lists. Thus they can be checked seperately, without rescanning the whole queue. - If a complex operation must sleep, then all pending change operations are moved into the global queue. This allows to keep everything FIFO. - When all complex operations have completed, the simple ops are moved back into the per-semaphore queues. Advantage: - FIFO. Dropping FIFO is a user visible change, and I'm a coward.
I am still not entirely convinced that FIFO is worthwhile, but the code looks correct to me. Acked-by: Rik van Riel <[email protected]>
- simpler check_restart logic. - Efficient handling of wait-for-zero semops, both simple and complex. - Fewer restarts in update_queue(), because pending wait-for-zero do not force a restart anymore. Other changes: - try_atomic_semop() also performs the semop. Thus rename the function. It passes tests with qemu, but not boot-tested due to EFI problems. Signed-off-by: Manfred Spraul <[email protected]>
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