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blockjob: reimplement block_job_sleep_ns to allow cancellation

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This reverts the effects of commit 4afeffc857 ("blockjob: do not allow
coroutine double entry or entry-after-completion", 2017-11-21)

This fixed the symptom of a bug rather than the root cause. Canceling the
wait on a sleeping blockjob coroutine is generally fine, we just need to
make it work correctly across AioContexts.  To do so, use a QEMUTimer
that calls block_job_enter.  Use a mutex to ensure that block_job_enter
synchronizes correctly with block_job_sleep_ns.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-By: Jeff Cody <jcody@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-11-29 11:25:13 +01:00 • committed by Kevin Wolf
parent 356f59b875
commit fc24908e7d
3 changed files with 61 additions and 14 deletions
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8
include/block/blockjob.h
View file

@ -77,7 +77,7 @@ typedef struct BlockJob {
/**
* Set to false by the job while the coroutine has yielded and may be
* re-entered by block_job_enter(). There may still be I/O or event loop
* activity pending.
* activity pending. Accessed under block_job_mutex (in blockjob.c).
*/
bool busy;
@ -135,6 +135,12 @@ typedef struct BlockJob {
*/
int ret;
/**
* Timer that is used by @block_job_sleep_ns. Accessed under
* block_job_mutex (in blockjob.c).
*/
QEMUTimer sleep_timer;
/** Non-NULL if this job is part of a transaction */
BlockJobTxn *txn;
QLIST_ENTRY(BlockJob) txn_list;

4
include/block/blockjob_int.h
View file

@ -142,8 +142,8 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
* @ns: How many nanoseconds to stop for.
*
* Put the job to sleep (assuming that it wasn't canceled) for @ns
* %QEMU_CLOCK_REALTIME nanoseconds. Canceling the job will not interrupt
* the wait, so the cancel will not process until the coroutine wakes up.
* %QEMU_CLOCK_REALTIME nanoseconds. Canceling the job will immediately
* interrupt the wait.
*/
void block_job_sleep_ns(BlockJob *job, int64_t ns);