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
---
include/block/blockjob.h | 13 +
include/qemu/job.h | 3 +++
blockjob.c | 18 ++
job.c| 7 +++
4 files changed, 41 insertions(+)
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index 32c00b7dc0..2290bbb824 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -70,6 +70,9 @@ typedef struct BlockJob {
/** Called when the job transitions to READY */
Notifier ready_notifier;
+/** Called when the job coroutine yields or terminates */
+Notifier idle_notifier;
+
/** BlockDriverStates that are involved in this block job */
GSList *nodes;
} BlockJob;
@@ -119,6 +122,16 @@ int block_job_add_bdrv(BlockJob *job, const char *name,
BlockDriverState *bs,
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:
* @job: The job to set the speed for.
* @speed: The new value
diff --git a/include/qemu/job.h b/include/qemu/job.h
index 18c9223e31..0dae5b8481 100644
--- a/include/qemu/job.h
+++ b/include/qemu/job.h
@@ -148,6 +148,9 @@ typedef struct Job {
/** Notifiers called when the job transitions to READY */
NotifierList on_ready;
+/** Notifiers called when the job coroutine yields or terminates */
+NotifierList on_idle;
+
/** Element of the list of jobs */
QLIST_ENTRY(Job) job_list;
diff --git a/blockjob.c b/blockjob.c
index be5903aa96..8d27e8e1ea 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -221,6 +221,22 @@ int block_job_add_bdrv(BlockJob *job, const char *name,
BlockDriverState *bs,
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)
{
return (job->job.id == NULL);
@@ -419,6 +435,7 @@ void *block_job_create(const char *job_id, const
BlockJobDriver *driver,
job->finalize_completed_notifier.notify = block_job_event_completed;
job->pending_notifier.notify = block_job_event_pending;
job->ready_notifier.notify = block_job_event_ready;
+job->idle_notifier.notify = block_job_on_idle;
notifier_list_add(>job.on_finalize_cancelled,
>finalize_cancelled_notifier);
@@ -426,6 +443,7 @@ void *block_job_create(const char *job_id, const
BlockJobDriver *driver,
>finalize_completed_notifier);
notifier_list_add(>job.on_pending, >pending_notifier);
notifier_list_add(>job.on_ready, >ready_notifier);
+notifier_list_add(>job.on_idle, >idle_notifier);
error_setg(>blocker, "block device is in use by block job: %s",
job_type_str(>job));
diff --git a/job.c b/job.c
index e36ebaafd8..9ad0b7476a 100644
--- a/job.c
+++ b/job.c
@@ -410,6 +410,11 @@ static void job_event_ready(Job *job)
notifier_list_notify(>on_ready, job);
}
+static void job_event_idle(Job *job)
+{
+notifier_list_notify(>on_idle, job);
+}
+
void job_enter_cond(Job *job, bool(*fn)(Job *job))
{
if (!job_started(job)) {
@@ -455,6 +460,7 @@ static void coroutine_fn job_do_yield(Job *job, uint64_t ns)
timer_mod(>sleep_timer, ns);
}
job->busy = false;
+job_event_idle(job);
job_unlock();
qemu_coroutine_yield();
@@ -547,6 +553,7 @@ static void coroutine_fn job_co_entry(void *opaque)
assert(job && job->driver && job->driver->start);
job_pause_point(job);
job->driver->start(job);
+job_event_idle(job);
}
--
2.13.6
