Hello, On Wed 02-03-16 11:00:58, Tejun Heo wrote: > On Fri, Feb 26, 2016 at 02:19:20PM +0800, Peter Chen wrote: > > On Thu, Feb 25, 2016 at 05:01:12PM -0500, Tejun Heo wrote: > > > Hello, Peter. > > > > > > On Wed, Feb 24, 2016 at 03:24:30PM +0800, Peter Chen wrote: > > > > > You might want to complain to the block-layer people about this. I > > > > > don't know if anything can be done to fix it. > > > > > > > > > > Or maybe flush_work and flush_delayed_work can be changed to avoid > > > > > blocking if the workqueue is frozen. Tejun? > > > > > > > > > > > > > I have a patch to show the root cause of this issue. > > > > > > > > http://www.spinics.net/lists/linux-usb/msg136815.html > > > > > > I don't get it. Why would it deadlock? Shouldn't things get rolling > > > once the workqueues are thawed? > > > > The workqueue writeback can't be thawed due to driver's resume > > (dpm_complete) is lock nested, and can't be finished. > > Ugh... that's nasty. I wonder whether the right thing to do is making > writeback workers non-freezable. IOs are supposed to be blocked from > lower layer anyway. Jan, what do you think? Well no, at least currently IO is not blocked in lower layers AFAIK - for that you'd need to freeze block devices & filesystems and there are issues with that (Jiri Kosina was the last one which was trying to make this work AFAIR). And I think you need to stop writeback (and generally any IO) to be generated so that it doesn't interact in a strange way with device drivers being frozen. So IMO until suspend freezes filesystems & devices properly you have to freeze writeback workqueue. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
