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From c933e15569c9d9b3db7031d8c54712f819816f39 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 14 Sep 2018 10:55:39 +0200
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Subject: [PATCH 48/49] job: Avoid deadlocks in job_completed_txn_abort()
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180914105540.18077-42-kwolf@redhat.com>
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Patchwork-id: 82194
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 41/42] job: Avoid deadlocks in job_completed_txn_abort()
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Bugzilla: 1601212
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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Amongst others, job_finalize_single() calls the .prepare/.commit/.abort
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callbacks of the individual job driver. Recently, their use was adapted
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for all block jobs so that they involve code calling AIO_WAIT_WHILE()
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now. Such code must be called under the AioContext lock for the
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respective job, but without holding any other AioContext lock.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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job.c | 16 +++++++++++-----
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1 file changed, 11 insertions(+), 5 deletions(-)
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diff --git a/job.c b/job.c
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index 42af9e2..5b53e43 100644
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--- a/job.c
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+++ b/job.c
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@@ -713,6 +713,7 @@ static void job_cancel_async(Job *job, bool force)
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static void job_completed_txn_abort(Job *job)
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{
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+ AioContext *outer_ctx = job->aio_context;
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AioContext *ctx;
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JobTxn *txn = job->txn;
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Job *other_job;
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@@ -726,23 +727,26 @@ static void job_completed_txn_abort(Job *job)
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txn->aborting = true;
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job_txn_ref(txn);
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- /* We are the first failed job. Cancel other jobs. */
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- QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
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- ctx = other_job->aio_context;
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- aio_context_acquire(ctx);
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- }
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+ /* We can only hold the single job's AioContext lock while calling
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+ * job_finalize_single() because the finalization callbacks can involve
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+ * calls of AIO_WAIT_WHILE(), which could deadlock otherwise. */
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+ aio_context_release(outer_ctx);
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/* Other jobs are effectively cancelled by us, set the status for
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* them; this job, however, may or may not be cancelled, depending
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* on the caller, so leave it. */
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QLIST_FOREACH(other_job, &txn->jobs, txn_list) {
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if (other_job != job) {
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+ ctx = other_job->aio_context;
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+ aio_context_acquire(ctx);
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job_cancel_async(other_job, false);
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+ aio_context_release(ctx);
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}
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}
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while (!QLIST_EMPTY(&txn->jobs)) {
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other_job = QLIST_FIRST(&txn->jobs);
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ctx = other_job->aio_context;
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+ aio_context_acquire(ctx);
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if (!job_is_completed(other_job)) {
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assert(job_is_cancelled(other_job));
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job_finish_sync(other_job, NULL, NULL);
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@@ -751,6 +755,8 @@ static void job_completed_txn_abort(Job *job)
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aio_context_release(ctx);
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}
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+ aio_context_acquire(outer_ctx);
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+
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job_txn_unref(txn);
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}
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--
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1.8.3.1
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