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[Qemu-block] [PATCH 1/5] blockjob: do not allow coroutine double entry o
From: |
Jeff Cody |
Subject: |
[Qemu-block] [PATCH 1/5] blockjob: do not allow coroutine double entry or entry-after-completion |
Date: |
Sun, 19 Nov 2017 21:46:42 -0500 |
When block_job_sleep_ns() is called, the co-routine is scheduled for
future execution. If we allow the job to be re-entered prior to the
scheduled time, we present a race condition in which a coroutine can be
entered recursively, or even entered after the coroutine is deleted.
The job->busy flag is used by blockjobs when a coroutine is busy
executing. The function 'block_job_enter()' obeys the busy flag,
and will not enter a coroutine if set. If we sleep a job, we need to
leave the busy flag set, so that subsequent calls to block_job_enter()
are prevented.
This fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1508708
Also, in block_job_start(), set the relevant job flags (.busy, .paused)
before creating the coroutine, not just before executing it.
Signed-off-by: Jeff Cody <address@hidden>
---
blockjob.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/blockjob.c b/blockjob.c
index 3a0c491..e181295 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -291,10 +291,10 @@ void block_job_start(BlockJob *job)
{
assert(job && !block_job_started(job) && job->paused &&
job->driver && job->driver->start);
- job->co = qemu_coroutine_create(block_job_co_entry, job);
job->pause_count--;
job->busy = true;
job->paused = false;
+ job->co = qemu_coroutine_create(block_job_co_entry, job);
bdrv_coroutine_enter(blk_bs(job->blk), job->co);
}
@@ -797,11 +797,14 @@ void block_job_sleep_ns(BlockJob *job, QEMUClockType
type, int64_t ns)
return;
}
- job->busy = false;
+ /* We need to leave job->busy set here, because when we have
+ * put a coroutine to 'sleep', we have scheduled it to run in
+ * the future. We cannot enter that same coroutine again before
+ * it wakes and runs, otherwise we risk double-entry or entry after
+ * completion. */
if (!block_job_should_pause(job)) {
co_aio_sleep_ns(blk_get_aio_context(job->blk), type, ns);
}
- job->busy = true;
block_job_pause_point(job);
}
--
2.9.5
[Qemu-block] [PATCH 2/5] coroutine: abort if we try to enter coroutine scheduled for another ctx, Jeff Cody, 2017/11/19
[Qemu-block] [PATCH 3/5] coroutines: abort if we try to enter a still-sleeping coroutine, Jeff Cody, 2017/11/19