blockjob: Wake up BDS when job becomes idle

In the context of draining a BDS, the .drained_poll callback of block
jobs is called. If this returns true (i.e. there is still some activity
pending), the drain operation may call aio_poll() with blocking=true to
wait for completion.

As soon as the pending activity is completed and the job finally arrives
in a quiescent state (i.e. its coroutine either yields with busy=false
or terminates), the block job must notify the aio_poll() loop to wake
up, otherwise we get a deadlock if both are running in different
threads.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2018-08-17 14:53:05 +02:00
parent d1756c780b
commit 34dc97b9a0
4 changed files with 41 additions and 0 deletions

View File

@ -221,6 +221,22 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
return 0; return 0;
} }
void block_job_wakeup_all_bdrv(BlockJob *job)
{
GSList *l;
for (l = job->nodes; l; l = l->next) {
BdrvChild *c = l->data;
bdrv_wakeup(c->bs);
}
}
static void block_job_on_idle(Notifier *n, void *opaque)
{
BlockJob *job = opaque;
block_job_wakeup_all_bdrv(job);
}
bool block_job_is_internal(BlockJob *job) bool block_job_is_internal(BlockJob *job)
{ {
return (job->job.id == NULL); return (job->job.id == NULL);
@ -416,6 +432,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
job->finalize_completed_notifier.notify = block_job_event_completed; job->finalize_completed_notifier.notify = block_job_event_completed;
job->pending_notifier.notify = block_job_event_pending; job->pending_notifier.notify = block_job_event_pending;
job->ready_notifier.notify = block_job_event_ready; job->ready_notifier.notify = block_job_event_ready;
job->idle_notifier.notify = block_job_on_idle;
notifier_list_add(&job->job.on_finalize_cancelled, notifier_list_add(&job->job.on_finalize_cancelled,
&job->finalize_cancelled_notifier); &job->finalize_cancelled_notifier);
@ -423,6 +440,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
&job->finalize_completed_notifier); &job->finalize_completed_notifier);
notifier_list_add(&job->job.on_pending, &job->pending_notifier); notifier_list_add(&job->job.on_pending, &job->pending_notifier);
notifier_list_add(&job->job.on_ready, &job->ready_notifier); notifier_list_add(&job->job.on_ready, &job->ready_notifier);
notifier_list_add(&job->job.on_idle, &job->idle_notifier);
error_setg(&job->blocker, "block device is in use by block job: %s", error_setg(&job->blocker, "block device is in use by block job: %s",
job_type_str(&job->job)); job_type_str(&job->job));

View File

@ -70,6 +70,9 @@ typedef struct BlockJob {
/** Called when the job transitions to READY */ /** Called when the job transitions to READY */
Notifier ready_notifier; Notifier ready_notifier;
/** Called when the job coroutine yields or terminates */
Notifier idle_notifier;
/** BlockDriverStates that are involved in this block job */ /** BlockDriverStates that are involved in this block job */
GSList *nodes; GSList *nodes;
} BlockJob; } BlockJob;
@ -118,6 +121,16 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
*/ */
void block_job_remove_all_bdrv(BlockJob *job); void block_job_remove_all_bdrv(BlockJob *job);
/**
* block_job_wakeup_all_bdrv:
* @job: The block job
*
* Calls bdrv_wakeup() for all BlockDriverStates that have been added to the
* job. This function is to be called whenever child_job_drained_poll() would
* go from true to false to notify waiting drain requests.
*/
void block_job_wakeup_all_bdrv(BlockJob *job);
/** /**
* block_job_set_speed: * block_job_set_speed:
* @job: The job to set the speed for. * @job: The job to set the speed for.

View File

@ -156,6 +156,9 @@ typedef struct Job {
/** Notifiers called when the job transitions to READY */ /** Notifiers called when the job transitions to READY */
NotifierList on_ready; NotifierList on_ready;
/** Notifiers called when the job coroutine yields or terminates */
NotifierList on_idle;
/** Element of the list of jobs */ /** Element of the list of jobs */
QLIST_ENTRY(Job) job_list; QLIST_ENTRY(Job) job_list;

7
job.c
View File

@ -402,6 +402,11 @@ static void job_event_ready(Job *job)
notifier_list_notify(&job->on_ready, job); notifier_list_notify(&job->on_ready, job);
} }
static void job_event_idle(Job *job)
{
notifier_list_notify(&job->on_idle, job);
}
void job_enter_cond(Job *job, bool(*fn)(Job *job)) void job_enter_cond(Job *job, bool(*fn)(Job *job))
{ {
if (!job_started(job)) { if (!job_started(job)) {
@ -447,6 +452,7 @@ static void coroutine_fn job_do_yield(Job *job, uint64_t ns)
timer_mod(&job->sleep_timer, ns); timer_mod(&job->sleep_timer, ns);
} }
job->busy = false; job->busy = false;
job_event_idle(job);
job_unlock(); job_unlock();
qemu_coroutine_yield(); qemu_coroutine_yield();
@ -865,6 +871,7 @@ static void coroutine_fn job_co_entry(void *opaque)
assert(job && job->driver && job->driver->run); assert(job && job->driver && job->driver->run);
job_pause_point(job); job_pause_point(job);
job->ret = job->driver->run(job, &job->err); job->ret = job->driver->run(job, &job->err);
job_event_idle(job);
job->deferred_to_main_loop = true; job->deferred_to_main_loop = true;
aio_bh_schedule_oneshot(qemu_get_aio_context(), job_exit, job); aio_bh_schedule_oneshot(qemu_get_aio_context(), job_exit, job);
} }