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job: Context changes in job_completed_txn_abort()

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Finalizing the job may cause its AioContext to change.  This is noted by
job_exit(), which points at job_txn_apply() to take this fact into
account.

However, job_completed() does not necessarily invoke job_txn_apply()
(through job_completed_txn_success()), but potentially also
job_completed_txn_abort().  The latter stores the context in a local
variable, and so always acquires the same context at its end that it has
released in the beginning -- which may be a different context from the
one that job_exit() releases at its end.  If it is different, qemu
aborts ("qemu_mutex_unlock_impl: Operation not permitted").

Drop the local @outer_ctx variable from job_completed_txn_abort(), and
instead re-acquire the actual job's context at the end of the function,
so job_exit() will release the same.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20211006151940.214590-2-hreitz@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
This commit is contained in:
Hanna Reitz 2021-10-06 17:19:28 +02:00 committed by Vladimir Sementsov-Ogievskiy
parent a9515df4d6
commit d431131439
1 changed files with 17 additions and 5 deletions
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22
job.c
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@ -737,7 +737,6 @@ static void job_cancel_async(Job *job, bool force)
static void job_completed_txn_abort(Job *job)
{
AioContext *outer_ctx = job->aio_context;
AioContext *ctx;
JobTxn *txn = job->txn;
Job *other_job;
@ -751,10 +750,14 @@ static void job_completed_txn_abort(Job *job)
txn->aborting = true;
job_txn_ref(txn);
/* We can only hold the single job's AioContext lock while calling
/*
* We can only hold the single job's AioContext lock while calling
* job_finalize_single() because the finalization callbacks can involve
* calls of AIO_WAIT_WHILE(), which could deadlock otherwise. */
aio_context_release(outer_ctx);
* calls of AIO_WAIT_WHILE(), which could deadlock otherwise.
* Note that the job's AioContext may change when it is finalized.
*/
job_ref(job);
aio_context_release(job->aio_context);
/* Other jobs are effectively cancelled by us, set the status for
* them; this job, however, may or may not be cancelled, depending
@ -769,6 +772,10 @@ static void job_completed_txn_abort(Job *job)
}
while (!QLIST_EMPTY(&txn->jobs)) {
other_job = QLIST_FIRST(&txn->jobs);
/*
* The job's AioContext may change, so store it in @ctx so we
* release the same context that we have acquired before.
*/
ctx = other_job->aio_context;
aio_context_acquire(ctx);
if (!job_is_completed(other_job)) {
@ -779,7 +786,12 @@ static void job_completed_txn_abort(Job *job)
aio_context_release(ctx);
}
aio_context_acquire(outer_ctx);
/*
* Use job_ref()/job_unref() so we can read the AioContext here
* even if the job went away during job_finalize_single().
*/
aio_context_acquire(job->aio_context);
job_unref(job);
job_txn_unref(txn);
}