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? Alan Stern -- 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
