Messages in this thread | | | Date | Wed, 21 Nov 2012 00:31:51 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH v2 1/2] block: Remove deadlock in disk_clear_events |
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On Mon, 19 Nov 2012 18:07:01 -0800 Derek Basehore <dbasehore@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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