Commit 644f3a29 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

job: Avoid deadlocks in job_completed_txn_abort() 



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: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
parent ecc1a5c7

job.c

+11 −5
Original line number Diff line number Diff line
@@ -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);

}