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Fix race in POSIX AIO emulation (Jan Kiszka) 

When we cancel an AIO request that is already being processed by
aio_thread, qemu_paio_cancel should return QEMU_PAIO_NOTCANCELED as long
as aio_thread isn't done with this request. But as the latter currently
updates aiocb->ret after every block of the request, we may report
QEMU_PAIO_ALLDONE too early.

Futhermore, in case some zero-length request should have been queued,
aiocb->ret is never set to != -EINPROGRESS and callers like
raw_aio_cancel could get stuck in an endless loop.

Fix those issues by updating aiocb->ret _after_ the request has been
fully processed. This also simplifies the locking.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6278 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
aliguori 2009-01-13 15:13:53 +00:00
parent f48c144e24
commit f094a78220
1 changed files with 2 additions and 7 deletions
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9
posix-aio-compat.c
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@ -81,21 +81,16 @@ static void *aio_thread(void *unused)
if (len == -1 && errno == EINTR)
continue;
else if (len == -1) {
pthread_mutex_lock(&lock);
aiocb->ret = -errno;
pthread_mutex_unlock(&lock);
offset = -errno;
break;
} else if (len == 0)
break;
offset += len;
pthread_mutex_lock(&lock);
aiocb->ret = offset;
pthread_mutex_unlock(&lock);
}
pthread_mutex_lock(&lock);
aiocb->ret = offset;
idle_threads++;
pthread_mutex_unlock(&lock);