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job: Use AIO_WAIT_WHILE() in job_finish_sync()

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job_finish_sync() needs to release the AioContext lock of the job before
calling aio_poll(). Otherwise, callbacks called by aio_poll() would
possibly take the lock a second time and run into a deadlock with a
nested AIO_WAIT_WHILE() call.

Also, job_drain() without aio_poll() isn't necessarily enough to make
progress on a job, it could depend on bottom halves to be executed.

Combine both open-coded while loops into a single AIO_WAIT_WHILE() call
that solves both of these problems.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2018-08-17 14:58:49 +02:00
parent 30c070a547
commit de0fbe6480
1 changed files with 6 additions and 8 deletions
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14
job.c
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@ -29,6 +29,7 @@
#include "qemu/job.h"
#include "qemu/id.h"
#include "qemu/main-loop.h"
#include "block/aio-wait.h"
#include "trace-root.h"
#include "qapi/qapi-events-job.h"
@ -962,6 +963,7 @@ void job_complete(Job *job, Error **errp)
int job_finish_sync(Job *job, void (*finish)(Job *, Error **errp), Error **errp)
{
Error *local_err = NULL;
AioWait dummy_wait = {};
int ret;
job_ref(job);
@ -974,14 +976,10 @@ int job_finish_sync(Job *job, void (*finish)(Job *, Error **errp), Error **errp)
job_unref(job);
return -EBUSY;
}
/* job_drain calls job_enter, and it should be enough to induce progress
* until the job completes or moves to the main thread. */
while (!job->deferred_to_main_loop && !job_is_completed(job)) {
job_drain(job);
}
while (!job_is_completed(job)) {
aio_poll(qemu_get_aio_context(), true);
}
AIO_WAIT_WHILE(&dummy_wait, job->aio_context,
(job_drain(job), !job_is_completed(job)));
ret = (job_is_cancelled(job) && job->ret == 0) ? -ECANCELED : job->ret;
job_unref(job);
return ret;