On Mon, 19 Nov 2012 18:07:01 -0800 Derek Basehore <dbaseh...@chromium.org>
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.
um,
- this is identical to v1
- ten days ago Jens said "thanks, applied" to v1, but it isn't in linux-next.
- At that time Jens asked you whether a -stable backport was
warranted but I see no reply on that topic.
> --- 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
Like this:
/*
* We need to ...
> + * 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
s/worqueue/workqueue/
> + * 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);
--
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