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From 2a9333d5c086c587c527afe9dc9936e3a1658e84 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 10:55:23 +0200
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Subject: [PATCH 32/49] job: Fix nested aio_poll() hanging in job_txn_apply
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180914105540.18077-26-kwolf@redhat.com>
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Patchwork-id: 82177
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 25/42] job: Fix nested aio_poll() hanging in job_txn_apply
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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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From: Fam Zheng <famz@redhat.com>
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All callers have acquired ctx already. Doing that again results in
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aio_poll() hang. This fixes the problem that a BDRV_POLL_WHILE() in the
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callback cannot make progress because ctx is recursively locked, for
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example, when drive-backup finishes.
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There are two callers of job_finalize():
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fam@lemon:~/work/qemu [master]$ git grep -w -A1 '^\s*job_finalize'
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blockdev.c: job_finalize(&job->job, errp);
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blockdev.c- aio_context_release(aio_context);
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--
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job-qmp.c: job_finalize(job, errp);
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job-qmp.c- aio_context_release(aio_context);
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--
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tests/test-blockjob.c: job_finalize(&job->job, &error_abort);
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tests/test-blockjob.c- assert(job->job.status == JOB_STATUS_CONCLUDED);
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Ignoring the test, it's easy to see both callers to job_finalize (and
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job_do_finalize) have acquired the context.
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Cc: qemu-stable@nongnu.org
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Reported-by: Gu Nini <ngu@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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job.c | 18 +++++-------------
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1 file changed, 5 insertions(+), 13 deletions(-)
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diff --git a/job.c b/job.c
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index dfba4bc..5d117fb 100644
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--- a/job.c
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+++ b/job.c
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@@ -136,21 +136,13 @@ static void job_txn_del_job(Job *job)
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}
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}
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-static int job_txn_apply(JobTxn *txn, int fn(Job *), bool lock)
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+static int job_txn_apply(JobTxn *txn, int fn(Job *))
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{
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- AioContext *ctx;
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Job *job, *next;
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int rc = 0;
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QLIST_FOREACH_SAFE(job, &txn->jobs, txn_list, next) {
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- if (lock) {
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- ctx = job->aio_context;
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- aio_context_acquire(ctx);
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- }
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rc = fn(job);
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- if (lock) {
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- aio_context_release(ctx);
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- }
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if (rc) {
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break;
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}
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@@ -775,11 +767,11 @@ static void job_do_finalize(Job *job)
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assert(job && job->txn);
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/* prepare the transaction to complete */
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- rc = job_txn_apply(job->txn, job_prepare, true);
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+ rc = job_txn_apply(job->txn, job_prepare);
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if (rc) {
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job_completed_txn_abort(job);
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} else {
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- job_txn_apply(job->txn, job_finalize_single, true);
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+ job_txn_apply(job->txn, job_finalize_single);
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}
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}
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@@ -825,10 +817,10 @@ static void job_completed_txn_success(Job *job)
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assert(other_job->ret == 0);
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}
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- job_txn_apply(txn, job_transition_to_pending, false);
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+ job_txn_apply(txn, job_transition_to_pending);
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/* If no jobs need manual finalization, automatically do so */
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- if (job_txn_apply(txn, job_needs_finalize, false) == 0) {
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+ if (job_txn_apply(txn, job_needs_finalize) == 0) {
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job_do_finalize(job);
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}
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}
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--
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1.8.3.1
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