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Re: [Qemu-devel] Hang in aio/multi/mutex/mcs
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] Hang in aio/multi/mutex/mcs |
Date: |
Fri, 24 Feb 2017 18:08:29 +0000 |
User-agent: |
mu4e 0.9.19; emacs 25.2.5 |
Paolo Bonzini <address@hidden> writes:
> On 23/02/2017 20:48, Alex Bennée wrote:
>> Hope that helps the debugging ;-)
>
> Worst case we can just remove the test (it's only there for performance
> comparison, not a bug in actual QEMU code), but this seems to help here:
>
> diff --git a/tests/test-aio-multithread.c b/tests/test-aio-multithread.c
> index f11e990..8b0b40e 100644
> --- a/tests/test-aio-multithread.c
> +++ b/tests/test-aio-multithread.c
> @@ -309,7 +309,7 @@ static void mcs_mutex_lock(void)
> static void mcs_mutex_unlock(void)
> {
> int next;
> - if (nodes[id].next == -1) {
> + if (atomic_read(&nodes[id].next) == -1) {
> if (atomic_read(&mutex_head) == id &&
> atomic_cmpxchg(&mutex_head, id, -1) == id) {
> /* Last item in the list, exit. */
> @@ -323,7 +323,7 @@ static void mcs_mutex_unlock(void)
> }
>
> /* Wake up the next in line. */
> - next = nodes[id].next;
> + next = atomic_read(&nodes[id].next);
> nodes[next].locked = 0;
> qemu_futex_wake(&nodes[next].locked, 1);
> }
Well it certainly looks like it improves the results on Travis.
Tested-by: Alex Bennée <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
--
Alex Bennée