jobs: group together API calls under the same job lock

Now that the API offers also _locked() functions, take advantage
of it and give also the caller control to take the lock and call
_locked functions.

This makes sense especially when we have for loops, because it
makes no sense to have:

for(job = job_next(); ...)

where each job_next() takes the lock internally.
Instead we want

JOB_LOCK_GUARD();
for(job = job_next_locked(); ...)

In addition, protect also direct field accesses, by either creating a
new critical section or widening the existing ones.

Note: at this stage, job_{lock/unlock} and job lock guard macros
are *nop*.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20220926093214.506243-12-eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -4981,8 +4981,8 @@ static void bdrv_close(BlockDriverState *bs)
 
 void bdrv_close_all(void)
 {
-    assert(job_next(NULL) == NULL);
     GLOBAL_STATE_CODE();
+    assert(job_next(NULL) == NULL);
 
     /* Drop references from requests still in flight, such as canceled block
      * jobs whose AIO context has not been polled yet */
@@ -6168,13 +6168,16 @@ XDbgBlockGraph *bdrv_get_xdbg_block_graph(Error **errp)
         }
     }
 
-    for (job = block_job_next(NULL); job; job = block_job_next(job)) {
-        GSList *el;
+    WITH_JOB_LOCK_GUARD() {
+        for (job = block_job_next_locked(NULL); job;
+             job = block_job_next_locked(job)) {
+            GSList *el;
 
-        xdbg_graph_add_node(gr, job, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_JOB,
-                           job->job.id);
-        for (el = job->nodes; el; el = el->next) {
-            xdbg_graph_add_edge(gr, job, (BdrvChild *)el->data);
+            xdbg_graph_add_node(gr, job, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_JOB,
+                                job->job.id);
+            for (el = job->nodes; el; el = el->next) {
+                xdbg_graph_add_edge(gr, job, (BdrvChild *)el->data);
+            }
         }
     }
 

blockdev.c

@@ -150,12 +150,15 @@ void blockdev_mark_auto_del(BlockBackend *blk)
         return;
     }
 
-    for (job = block_job_next(NULL); job; job = block_job_next(job)) {
+    JOB_LOCK_GUARD();
+
+    for (job = block_job_next_locked(NULL); job;
+         job = block_job_next_locked(job)) {
         if (block_job_has_bdrv(job, blk_bs(blk))) {
             AioContext *aio_context = job->job.aio_context;
             aio_context_acquire(aio_context);
 
-            job_cancel(&job->job, false);
+            job_cancel_locked(&job->job, false);
 
             aio_context_release(aio_context);
         }
@@ -3756,7 +3759,10 @@ BlockJobInfoList *qmp_query_block_jobs(Error **errp)
     BlockJobInfoList *head = NULL, **tail = &head;
     BlockJob *job;
 
-    for (job = block_job_next(NULL); job; job = block_job_next(job)) {
+    JOB_LOCK_GUARD();
+
+    for (job = block_job_next_locked(NULL); job;
+         job = block_job_next_locked(job)) {
         BlockJobInfo *value;
         AioContext *aio_context;
 
@@ -3765,7 +3771,7 @@ BlockJobInfoList *qmp_query_block_jobs(Error **errp)
         }
         aio_context = block_job_get_aio_context(job);
         aio_context_acquire(aio_context);
-        value = block_job_query(job, errp);
+        value = block_job_query_locked(job, errp);
         aio_context_release(aio_context);
         if (!value) {
             qapi_free_BlockJobInfoList(head);

blockjob.c

@@ -111,8 +111,10 @@ static bool child_job_drained_poll(BdrvChild *c)
     /* An inactive or completed job doesn't have any pending requests. Jobs
      * with !job->busy are either already paused or have a pause point after
      * being reentered, so no job driver code will run before they pause. */
-    if (!job->busy || job_is_completed(job)) {
-        return false;
+    WITH_JOB_LOCK_GUARD() {
+        if (!job->busy || job_is_completed_locked(job)) {
+            return false;
+        }
     }
 
     /* Otherwise, assume that it isn't fully stopped yet, but allow the job to
@@ -475,13 +477,15 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
     job->ready_notifier.notify = block_job_event_ready;
     job->idle_notifier.notify = block_job_on_idle;
 
-    notifier_list_add(&job->job.on_finalize_cancelled,
-                      &job->finalize_cancelled_notifier);
-    notifier_list_add(&job->job.on_finalize_completed,
-                      &job->finalize_completed_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_idle, &job->idle_notifier);
+    WITH_JOB_LOCK_GUARD() {
+        notifier_list_add(&job->job.on_finalize_cancelled,
+                          &job->finalize_cancelled_notifier);
+        notifier_list_add(&job->job.on_finalize_completed,
+                          &job->finalize_completed_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_idle, &job->idle_notifier);
+    }
 
     error_setg(&job->blocker, "block device is in use by block job: %s",
                job_type_str(&job->job));
@@ -558,10 +562,15 @@ BlockErrorAction block_job_error_action(BlockJob *job, BlockdevOnError on_err,
                                         action);
     }
     if (action == BLOCK_ERROR_ACTION_STOP) {
-        if (!job->job.user_paused) {
-            job_pause(&job->job);
-            /* make the pause user visible, which will be resumed from QMP. */
-            job->job.user_paused = true;
+        WITH_JOB_LOCK_GUARD() {
+            if (!job->job.user_paused) {
+                job_pause_locked(&job->job);
+                /*
+                 * make the pause user visible, which will be
+                 * resumed from QMP.
+                 */
+                job->job.user_paused = true;
+            }
         }
         block_job_iostatus_set_err(job, error);
     }

job-qmp.c

@@ -164,7 +164,8 @@ void qmp_job_dismiss(const char *id, Error **errp)
     aio_context_release(aio_context);
 }
 
-static JobInfo *job_query_single(Job *job, Error **errp)
+/* Called with job_mutex held. */
+static JobInfo *job_query_single_locked(Job *job, Error **errp)
 {
     JobInfo *info;
     uint64_t progress_current;
@@ -194,7 +195,9 @@ JobInfoList *qmp_query_jobs(Error **errp)
     JobInfoList *head = NULL, **tail = &head;
     Job *job;
 
-    for (job = job_next(NULL); job; job = job_next(job)) {
+    JOB_LOCK_GUARD();
+
+    for (job = job_next_locked(NULL); job; job = job_next_locked(job)) {
         JobInfo *value;
         AioContext *aio_context;
 
@@ -203,7 +206,7 @@ JobInfoList *qmp_query_jobs(Error **errp)
         }
         aio_context = job->aio_context;
         aio_context_acquire(aio_context);
-        value = job_query_single(job, errp);
+        value = job_query_single_locked(job, errp);
         aio_context_release(aio_context);
         if (!value) {
             qapi_free_JobInfoList(head);

monitor/qmp-cmds.c

@@ -135,8 +135,11 @@ void qmp_cont(Error **errp)
         blk_iostatus_reset(blk);
     }
 
-    for (job = block_job_next(NULL); job; job = block_job_next(job)) {
-        block_job_iostatus_reset(job);
+    WITH_JOB_LOCK_GUARD() {
+        for (job = block_job_next_locked(NULL); job;
+             job = block_job_next_locked(job)) {
+            block_job_iostatus_reset_locked(job);
+        }
     }
 
     /* Continuing after completed migration. Images have been inactivated to

qemu-img.c

@@ -912,9 +912,11 @@ static void run_block_job(BlockJob *job, Error **errp)
     int ret = 0;
 
     aio_context_acquire(aio_context);
-    job_ref(&job->job);
+    job_lock();
+    job_ref_locked(&job->job);
     do {
         float progress = 0.0f;
+        job_unlock();
         aio_poll(aio_context, true);
 
         progress_get_snapshot(&job->job.progress, &progress_current,
@@ -923,14 +925,17 @@ static void run_block_job(BlockJob *job, Error **errp)
             progress = (float)progress_current / progress_total * 100.f;
         }
         qemu_progress_print(progress, 0);
-    } while (!job_is_ready(&job->job) && !job_is_completed(&job->job));
+        job_lock();
+    } while (!job_is_ready_locked(&job->job) &&
+             !job_is_completed_locked(&job->job));
 
-    if (!job_is_completed(&job->job)) {
-        ret = job_complete_sync(&job->job, errp);
+    if (!job_is_completed_locked(&job->job)) {
+        ret = job_complete_sync_locked(&job->job, errp);
     } else {
         ret = job->job.ret;
     }
-    job_unref(&job->job);
+    job_unref_locked(&job->job);
+    job_unlock();
     aio_context_release(aio_context);
 
     /* publish completion progress only when success */