On Tue, Aug 27, 2019 at 03:36:34PM +0100, Russell King - ARM Linux admin wrote: > On Tue, Aug 27, 2019 at 03:55:23PM +0200, Ulf Hansson wrote: > > On Tue, 27 Aug 2019 at 15:43, Russell King - ARM Linux admin > > <linux@xxxxxxxxxxxxxxx> wrote: > > > > > > Hi, > > > > > > While dd'ing the contents of a SD card, I get hung task timeout > > > messages as per below. However, the dd is making progress. Any > > > ideas? > > > > > > Presumably, mmc_rescan doesn't get a look-in while IO is progressing > > > for the card? > > > > Is it a regression? > > > > There not much of recent mmc core and mmc block changes, that I can > > think of at this point. > > No idea - I just repaired the SD socket after the D2 line became > disconnected, and decided to run that command as a test. > > > > ARM64 host, Macchiatobin, uSD card. > > > > What mmc host driver is it? mmci? > > sdhci-xenon. > > I'm just trying with one CPU online, then I'll try with two. My > suspicion is that there's a problem in the ARM64 arch code where > unlocking a mutex doesn't get noticed on other CPUs. > > Hmm, I thought I'd try bringing another CPU online, but it seems > like the ARM64 CPU hotplug code is broken: > > [ 3552.029689] CPU1: shutdown > [ 3552.031099] psci: CPU1 killed. > [ 3949.835212] CPU1: failed to come online > [ 3949.837753] CPU1: failed in unknown state : 0x0 > > which means I can only take CPUs down, I can't bring them back > online without rebooting. Okay, running on a single CPU shows no problems. Running on four CPUs (as originally) shows that the kworker thread _never_ gets scheduled, so the warning is not false. With three CPUs, same problem. root@arm-d06300000000:~# ps aux | grep ' D ' root 34 0.0 0.0 0 0 ? D 15:38 0:00 [kworker/1:1+events_freezable] root@arm-d06300000000:~# cat /proc/34/sched kworker/1:1 (34, #threads: 1) ------------------------------------------------------------------- se.exec_start : 318689.992440 se.vruntime : 37750.882357 se.sum_exec_runtime : 9.421240 se.nr_migrations : 0 nr_switches : 1174 nr_voluntary_switches : 1171 nr_involuntary_switches : 3 se.load.weight : 1048576 se.runnable_weight : 1048576 se.avg.load_sum : 6 se.avg.runnable_load_sum : 6 se.avg.util_sum : 5170 se.avg.load_avg : 0 se.avg.runnable_load_avg : 0 se.avg.util_avg : 0 se.avg.last_update_time : 318689991680 se.avg.util_est.ewma : 10 se.avg.util_est.enqueued : 0 policy : 0 prio : 120 clock-delta : 0 The only thing that changes there is "clock-delta". When I kill the dd, I get: root@arm-d06300000000:~# cat /proc/34/sched kworker/1:1 (34, #threads: 1) ------------------------------------------------------------------- se.exec_start : 574025.791680 se.vruntime : 79996.657300 se.sum_exec_runtime : 10.916400 se.nr_migrations : 0 nr_switches : 1403 nr_voluntary_switches : 1400 nr_involuntary_switches : 3 se.load.weight : 1048576 se.runnable_weight : 1048576 se.avg.load_sum : 15 se.avg.runnable_load_sum : 15 se.avg.util_sum : 15007 se.avg.load_avg : 0 se.avg.runnable_load_avg : 0 se.avg.util_avg : 0 se.avg.last_update_time : 574025791488 se.avg.util_est.ewma : 10 se.avg.util_est.enqueued : 0 policy : 0 prio : 120 clock-delta : 40 so the thread makes forward progress. Down to two CPUs: root@arm-d06300000000:~# ps aux | grep ' D ' root 34 0.0 0.0 0 0 ? D 15:38 0:00 [kworker/1:1+events_freezable] Same symptoms. dd and md5sum switch between CPU 0 and CPU1. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
