109 lines
3.7 KiB
Diff
109 lines
3.7 KiB
Diff
From 17511eb281e005da6e617acd12c81a0a1fa1771d Mon Sep 17 00:00:00 2001
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From: John Snow <jsnow@redhat.com>
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Date: Tue, 25 Sep 2018 22:34:09 +0100
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Subject: jobs: add exit shim
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RH-Author: John Snow <jsnow@redhat.com>
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Message-id: <20180925223431.24791-4-jsnow@redhat.com>
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Patchwork-id: 82273
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O-Subject: [RHEL8/rhel qemu-kvm PATCH 03/25] jobs: add exit shim
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Bugzilla: 1632939
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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All jobs do the same thing when they leave their running loop:
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- Store the return code in a structure
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- wait to receive this structure in the main thread
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- signal job completion via job_completed
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Few jobs do anything beyond exactly this. Consolidate this exit
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logic for a net reduction in SLOC.
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More seriously, when we utilize job_defer_to_main_loop_bh to call
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a function that calls job_completed, job_finalize_single will run
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in a context where it has recursively taken the aio_context lock,
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which can cause hangs if it puts down a reference that causes a flush.
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You can observe this in practice by looking at mirror_exit's careful
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placement of job_completed and bdrv_unref calls.
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If we centralize job exiting, we can signal job completion from outside
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of the aio_context, which should allow for job cleanup code to run with
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only one lock, which makes cleanup callbacks less tricky to write.
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Signed-off-by: John Snow <jsnow@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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Message-id: 20180830015734.19765-4-jsnow@redhat.com
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Reviewed-by: Jeff Cody <jcody@redhat.com>
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit 00359a71d45a414ee47d8e423104dc0afd24ec65)
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Signed-off-by: John Snow <jsnow@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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include/qemu/job.h | 11 +++++++++++
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job.c | 18 ++++++++++++++++++
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2 files changed, 29 insertions(+)
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diff --git a/include/qemu/job.h b/include/qemu/job.h
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index e0e9987..1144d67 100644
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--- a/include/qemu/job.h
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+++ b/include/qemu/job.h
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@@ -209,6 +209,17 @@ struct JobDriver {
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void (*drain)(Job *job);
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/**
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+ * If the callback is not NULL, exit will be invoked from the main thread
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+ * when the job's coroutine has finished, but before transactional
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+ * convergence; before @prepare or @abort.
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+ *
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+ * FIXME TODO: This callback is only temporary to transition remaining jobs
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+ * to prepare/commit/abort/clean callbacks and will be removed before 3.1.
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+ * is released.
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+ */
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+ void (*exit)(Job *job);
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+
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+ /**
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* If the callback is not NULL, prepare will be invoked when all the jobs
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* belonging to the same transaction complete; or upon this job's completion
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* if it is not in a transaction.
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diff --git a/job.c b/job.c
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index 276024a..abe91af 100644
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--- a/job.c
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+++ b/job.c
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@@ -535,6 +535,18 @@ void job_drain(Job *job)
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}
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}
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+static void job_exit(void *opaque)
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+{
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+ Job *job = (Job *)opaque;
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+ AioContext *aio_context = job->aio_context;
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+
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+ if (job->driver->exit) {
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+ aio_context_acquire(aio_context);
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+ job->driver->exit(job);
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+ aio_context_release(aio_context);
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+ }
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+ job_completed(job, job->ret);
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+}
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/**
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* All jobs must allow a pause point before entering their job proper. This
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@@ -547,6 +559,12 @@ static void coroutine_fn job_co_entry(void *opaque)
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assert(job && job->driver && job->driver->run);
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job_pause_point(job);
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job->ret = job->driver->run(job, &job->err);
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+ if (!job->deferred_to_main_loop) {
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+ job->deferred_to_main_loop = true;
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+ aio_bh_schedule_oneshot(qemu_get_aio_context(),
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+ job_exit,
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+ 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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