The patch titled
Subject: block: remove deadlock in disk_clear_events
has been added to the -mm tree. Its filename is
block-remove-deadlock-in-disk_clear_events.patch
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------------------------------------------------------
From: Derek Basehore <dbasehore@xxxxxxxxxxxx>
Subject: block: remove deadlock in disk_clear_events
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.
Signed-off-by: Derek Basehore <dbasehore@xxxxxxxxxxxx>
Reviewed-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
block/genhd.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff -puN block/genhd.c~block-remove-deadlock-in-disk_clear_events block/genhd.c
--- a/block/genhd.c~block-remove-deadlock-in-disk_clear_events
+++ a/block/genhd.c
@@ -1565,7 +1565,13 @@ unsigned int disk_clear_events(struct ge
/* 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);
_
Patches currently in -mm which might be from dbasehore@xxxxxxxxxxxx are
linux-next.patch
block-remove-deadlock-in-disk_clear_events.patch
block-remove-deadlock-in-disk_clear_events-fix.patch
block-prevent-race-cleanup.patch
block-prevent-race-cleanup-fix.patch
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