On Tue, Feb 23, 2016 at 10:34:09AM -0500, Alan Stern wrote: > On Tue, 23 Feb 2016, Peter Chen wrote: > > > Hi Tejun Heo and Florian Mickler, > > > > I have a question that during the system resume process, the freezable > > workqueue can be thawed if there is a non-freezable workqueue is > > blocked (At uninterruptable state)? > > > > My case like below, I have a USB OTG (Micro-AB) cable is at USB > > Micro-B port, and there is a USB driver on it, and un-plug this > > cable can wake up system from the suspend. There is a non-freezable > > workqueue ci_otg will be scheduled after disconnecting OTG cable, > > and in its worker ci_otg_work, it will try to disconnect USB drive, > > and flush disk information. > > These operations probably are not safe while the system is resuming. > It might be best to make them wait until the resume is finished. > > > But flush disk information is done by > > freezable workqueue writeback, it seeems workqueue writeback is > > never got chance to execute, the workqueue ci_otg is waiting there > > forever, and the system is deadlock. > > > Both change workqueue ci_otg as freezable or change workqueue writeback > > as non-freezable can fix this problem. > > It sounds like making ci_otg freezable is the easiest solution. > > > Please ignore it, the system is locked at driver's resume, > > maybe at scsi or usb driver, so of cos, the freezable processes > > can't be thawed. > > > > [ 555.263177] [<c0043b1c>] (flush_work) from [<c0043fac>] (flush_delayed_work+0x48/0x4c) > > > [ 555.271106] r8:ed5b5000 r7:c0b38a3c r6:eea439cc r5:eea4372c r4:eea4372c > > > [ 555.277958] [<c0043f64>] (flush_delayed_work) from [<c00eae18>] (bdi_unregister+0x84/0xec) > > > [ 555.286236] r4:eea43520 r3:20000153 > > > [ 555.289885] [<c00ead94>] (bdi_unregister) from [<c02c2154>] (blk_cleanup_queue+0x180/0x29c) > > > [ 555.298250] r5:eea43808 r4:eea43400 > > 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 -- Best Regards, Peter Chen -- 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
