Re: [PATCH 1/2] PM: runtime: Fix I/O hang due to race between resume and runtime disable

[YangYang]

On 2025/11/27 2:40, Bart Van Assche wrote:
> On 11/26/25 7:41 AM, Rafael J. Wysocki wrote:
> > As it stands, you have a basic problem with respect to system
> > suspend/hibernation.  As I said before, the PM workqueue is frozen
> > during system suspend/hibernation transitions, so waiting for an async
> > resume request to complete then is pointless.
>
> Agreed. I noticed that any attempt to call request_firmware() from
> driver system resume callback functions causes a deadlock if these
> calls happen before the block device has been resumed.
>
> Thanks,
>
> Bart.

Does this patch look reasonable to you? It hasn't been fully tested 
yet, but the resume is now performed synchronously.

diff --git a/block/blk-core.c b/block/blk-core.c
index 66fb2071d..041d29ba4 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -323,12 +323,15 @@ int blk_queue_enter(struct request_queue *q, 
blk_mq_req_flags_t flags)
                 * reordered.
                 */
                smp_rmb();
-               wait_event(q->mq_freeze_wq,
-                          (!q->mq_freeze_depth &&
-                           blk_pm_resume_queue(pm, q)) ||
-                          blk_queue_dying(q));
+check:
+               wait_event(q->mq_freeze_wq, !q->mq_freeze_depth);
+
                if (blk_queue_dying(q))
                        return -ENODEV;
+               if (!blk_pm_resume_queue(pm, q)) {
+                       pm_runtime_resume(q->dev);
+                       goto check;
+               }
        }

        rwsem_acquire_read(&q->q_lockdep_map, 0, 0, _RET_IP_);
@@ -356,12 +359,15 @@ int __bio_queue_enter(struct request_queue *q, 
struct bio *bio)
                 * reordered.
                 */
                smp_rmb();
-               wait_event(q->mq_freeze_wq,
-                          (!q->mq_freeze_depth &&
-                           blk_pm_resume_queue(false, q)) ||
-                          test_bit(GD_DEAD, &disk->state));
+check:
+               wait_event(q->mq_freeze_wq, !q->mq_freeze_depth);
+
                if (test_bit(GD_DEAD, &disk->state))
                        goto dead;
+               if (!blk_pm_resume_queue(false, q)) {
+                       pm_runtime_resume(q->dev);
+                       goto check;
+               }
        }

        rwsem_acquire_read(&q->io_lockdep_map, 0, 0, _RET_IP_);
diff --git a/block/blk-pm.h b/block/blk-pm.h
index 8a5a0d4b3..c28fad105 100644
--- a/block/blk-pm.h
+++ b/block/blk-pm.h
@@ -12,7 +12,6 @@ static inline int blk_pm_resume_queue(const bool pm, 
struct request_queue *q)
                return 1;       /* Nothing to do */
        if (pm && q->rpm_status != RPM_SUSPENDED)
                return 1;       /* Request allowed */
-       pm_request_resume(q->dev);
        return 0;
 }