In disk_clear_events, do not put work on system_nrt_freezable_wq. Instead, put
it on system_nrt_wq.
There is a race between probing a usb and suspending the device. Since probing a
usb calls disk_clear_events, which puts work on a frozen workqueue, probing
cannot finish after the workqueue is frozen. However, suspending cannot finish
until the usb probe is finished, so we get a deadlock.
Change-Id: I05bc8f608f1c86b7efaca5c12e544dbd08dfaba4
Signed-off-by: Derek Basehore <[email protected]>
---
block/genhd.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 6cace66..4e700ee 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1571,7 +1571,13 @@ unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask)
/* uncondtionally schedule event check and wait for it to finish */
disk_block_events(disk);
- queue_delayed_work(system_freezable_wq, &ev->dwork, 0);
+ /* We need to put the work on system_nrt_wq here since there is a
+ * deadlock that happens while probing a usb device while suspending. If
+ * we put work on a freezable worqueue here, a usb probe will wait here
+ * until the workqueue is unfrozen during suspend. Since suspend waits
+ * on all probes to complete, we have a deadlock
+ */
+ queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
flush_delayed_work(&ev->dwork);
__disk_unblock_events(disk, false);
--
1.7.7.3
On 2012-10-11 15:52, Derek Basehore wrote:
> In disk_clear_events, do not put work on system_nrt_freezable_wq. Instead, put
> it on system_nrt_wq.
>
> There is a race between probing a usb and suspending the device. Since probing a
> usb calls disk_clear_events, which puts work on a frozen workqueue, probing
> cannot finish after the workqueue is frozen. However, suspending cannot finish
> until the usb probe is finished, so we get a deadlock.
Thanks, applied to later inclusion into 3.7. You did not mark this as
stable, though it seems it should be?
--
Jens Axboe