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job: Avoid deadlocks in job_completed_txn_abort()

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Amongst others, job_finalize_single() calls the .prepare/.commit/.abort
callbacks of the individual job driver. Recently, their use was adapted
for all block jobs so that they involve code calling AIO_WAIT_WHILE()
now. Such code must be called under the AioContext lock for the
respective job, but without holding any other AioContext lock.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2018-09-13 14:35:27 +02:00
parent ecc1a5c790
commit 644f3a29bd
1 changed files with 11 additions and 5 deletions
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16
job.c
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@ -718,6 +718,7 @@ 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;
@ -731,23 +732,26 @@ static void job_completed_txn_abort(Job *job)
txn->aborting = true;
job_txn_ref(txn);
/* We are the first failed job. Cancel other jobs. */
QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
ctx = other_job->aio_context;
aio_context_acquire(ctx);
}
/* 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);
/* Other jobs are effectively cancelled by us, set the status for
* them; this job, however, may or may not be cancelled, depending
* on the caller, so leave it. */
QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
if (other_job != job) {
ctx = other_job->aio_context;
aio_context_acquire(ctx);
job_cancel_async(other_job, false);
aio_context_release(ctx);
}
}
while (!QLIST_EMPTY(&txn->jobs)) {
other_job = QLIST_FIRST(&txn->jobs);
ctx = other_job->aio_context;
aio_context_acquire(ctx);
if (!job_is_completed(other_job)) {
assert(job_is_cancelled(other_job));
job_finish_sync(other_job, NULL, NULL);
@ -756,6 +760,8 @@ static void job_completed_txn_abort(Job *job)
aio_context_release(ctx);
}
aio_context_acquire(outer_ctx);
job_txn_unref(txn);
}