diff options
author | Jeff Cody <jcody@redhat.com> | 2017-11-17 22:26:16 -0500 |
---|---|---|
committer | Jeff Cody <jcody@redhat.com> | 2017-11-21 11:51:18 -0500 |
commit | 4afeffc8572f40d8844b946a30c00b10da4442b1 (patch) | |
tree | f877425b21bc20e94e3560a3036ebe15be460a7a /blockjob.c | |
parent | 7c3d1917fd7a3de906170fa3d6d3d4c5918b1e49 (diff) |
blockjob: do not allow coroutine double entry or entry-after-completion
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 changes the prior behavior of block_job_cancel() being able to
immediately wake up and cancel a job; in practice, this should not be an
issue, as the coroutine sleep times are generally very small, and the
cancel will occur the next time the coroutine wakes up.
This fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1508708
Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'blockjob.c')
-rw-r--r-- | blockjob.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/blockjob.c b/blockjob.c index 3a0c49137e..ff9a614531 100644 --- a/blockjob.c +++ b/blockjob.c @@ -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); } |