From bdc8bf786dcd258488ffd64fa37ecb0e801141ce Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 10 Oct 2018 20:21:54 +0100 Subject: [PATCH 28/49] job: Fix nested aio_poll() hanging in job_txn_apply RH-Author: Kevin Wolf Message-id: <20181010202213.7372-16-kwolf@redhat.com> Patchwork-id: 82605 O-Subject: [RHEL-8 qemu-kvm PATCH 25/44] job: Fix nested aio_poll() hanging in job_txn_apply Bugzilla: 1637976 RH-Acked-by: Max Reitz RH-Acked-by: John Snow RH-Acked-by: Thomas Huth From: Fam Zheng All callers have acquired ctx already. Doing that again results in aio_poll() hang. This fixes the problem that a BDRV_POLL_WHILE() in the callback cannot make progress because ctx is recursively locked, for example, when drive-backup finishes. There are two callers of job_finalize(): fam@lemon:~/work/qemu [master]$ git grep -w -A1 '^\s*job_finalize' blockdev.c: job_finalize(&job->job, errp); blockdev.c- aio_context_release(aio_context); -- job-qmp.c: job_finalize(job, errp); job-qmp.c- aio_context_release(aio_context); -- tests/test-blockjob.c: job_finalize(&job->job, &error_abort); tests/test-blockjob.c- assert(job->job.status == JOB_STATUS_CONCLUDED); Ignoring the test, it's easy to see both callers to job_finalize (and job_do_finalize) have acquired the context. Cc: qemu-stable@nongnu.org Reported-by: Gu Nini Reviewed-by: Eric Blake Signed-off-by: Fam Zheng Signed-off-by: Kevin Wolf (cherry picked from commit 49880165a44f26dc84651858750facdee31f2513) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- job.c | 18 +++++------------- 1 file changed, 5 insertions(+), 13 deletions(-) diff --git a/job.c b/job.c index dfba4bc..5d117fb 100644 --- a/job.c +++ b/job.c @@ -136,21 +136,13 @@ static void job_txn_del_job(Job *job) } } -static int job_txn_apply(JobTxn *txn, int fn(Job *), bool lock) +static int job_txn_apply(JobTxn *txn, int fn(Job *)) { - AioContext *ctx; Job *job, *next; int rc = 0; QLIST_FOREACH_SAFE(job, &txn->jobs, txn_list, next) { - if (lock) { - ctx = job->aio_context; - aio_context_acquire(ctx); - } rc = fn(job); - if (lock) { - aio_context_release(ctx); - } if (rc) { break; } @@ -775,11 +767,11 @@ static void job_do_finalize(Job *job) assert(job && job->txn); /* prepare the transaction to complete */ - rc = job_txn_apply(job->txn, job_prepare, true); + rc = job_txn_apply(job->txn, job_prepare); if (rc) { job_completed_txn_abort(job); } else { - job_txn_apply(job->txn, job_finalize_single, true); + job_txn_apply(job->txn, job_finalize_single); } } @@ -825,10 +817,10 @@ static void job_completed_txn_success(Job *job) assert(other_job->ret == 0); } - job_txn_apply(txn, job_transition_to_pending, false); + job_txn_apply(txn, job_transition_to_pending); /* If no jobs need manual finalization, automatically do so */ - if (job_txn_apply(txn, job_needs_finalize, false) == 0) { + if (job_txn_apply(txn, job_needs_finalize) == 0) { job_do_finalize(job); } } -- 1.8.3.1