On Wed, May 28, 2014 at 04:19:55AM +0100, Al Viro wrote: > On Tue, May 27, 2014 at 10:04:09AM +0300, Mika Westerberg wrote: > > On Tue, May 27, 2014 at 05:00:26AM +0100, Al Viro wrote: > > > On Tue, May 27, 2014 at 04:14:15AM +0100, Al Viro wrote: > > > > > > > As the matter of fact, let's try this instead - retry the same sucker > > > > immediately in case if trylocks fail. Comments? > > > > > > Better yet, let's take "move back to shrink list" into dentry_kill() > > > itself. Then we get consistent locking rules for dentry_kill() and > > > instead of unlock_on_failure we simply pass it NULL or the shrink > > > list to put the sucker back. Mika, could you test this one and see > > > if it fixes that livelock? The difference in behaviour is that in > > > case of trylock failure we hit that sucker again without letting > > > it ride all the way around the list, same as we do for other dentry_kill() > > > callers. > > > > I tried this patch and unfortunately it still results the same sort of > > livelock. I've attached the dmesg. > > > > I also tried the serialization patch from Linus and it seemed to fix the > > problem. After several rounds of USB memory stick plug/unplug I haven't > > seen a single "soft lockup" warning in dmesg. > > > > I'm able to reproduce the problem pretty easily, so if you have > > something else to try I'm more than happy to give it a try. > > Could you try this and post the resulting log? I'd really like to understand > what's going on there - are we really hitting trylock failures there and what > dentries are involved. I sent you the whole log privately so that I don't spam everyone. Summary is here: May 28 10:24:23 lahna kernel: scsi 14:0:0:0: Direct-Access JetFlash Transcend 4GB 8.07 PQ: 0 ANSI: 4 May 28 10:24:23 lahna kernel: sd 14:0:0:0: Attached scsi generic sg4 type 0 May 28 10:24:23 lahna kernel: sd 14:0:0:0: [sdc] 7864320 512-byte logical blocks: (4.02 GB/3.75 GiB) May 28 10:24:23 lahna kernel: sd 14:0:0:0: [sdc] Write Protect is off May 28 10:24:23 lahna kernel: sd 14:0:0:0: [sdc] Mode Sense: 23 00 00 00 May 28 10:24:23 lahna kernel: sd 14:0:0:0: [sdc] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA May 28 10:24:23 lahna kernel: sdc: sdc1 May 28 10:24:23 lahna kernel: sd 14:0:0:0: [sdc] Attached SCSI removable disk Here I detached the USB stick: May 28 10:24:32 lahna kernel: usb 3-10.4: USB disconnect, device number 6 May 28 10:24:32 lahna kernel: check_submounts_and_drop[/dev/block/8:33]; CPU 4 PID 576 [systemd-udevd] May 28 10:24:32 lahna kernel: dput[/dev/block/8:33]; CPU 4 PID 576 [systemd-udevd] May 28 10:24:32 lahna kernel: check_submounts_and_drop[3-10/3-10.4/3-10.4:1.0/host14]; CPU 1 PID 1683 [systemd-udevd] May 28 10:24:32 lahna kernel: shrink[3-10.4:1.0/host14/target14:0:0/subsystem]; CPU 1 PID 1683 [systemd-udevd] May 28 10:24:32 lahna kernel: shrink[host14/target14:0:0/14:0:0:0/rev]; CPU 1 PID 1683 [systemd-udevd] May 28 10:24:32 lahna kernel: shrink[host14/target14:0:0/14:0:0:0/vendor]; CPU 1 PID 1683 [systemd-udevd] May 28 10:24:32 lahna kernel: shrink[host14/target14:0:0/14:0:0:0/model]; CPU 1 PID 1683 [systemd-udevd] May 28 10:24:32 lahna kernel: check_submounts_and_drop[/dev/block/8:32]; CPU 4 PID 576 [systemd-udevd] ... May 28 10:24:32 lahna kernel: check_submounts_and_drop[0000:00:14.0/usb3/3-10/3-10.4]; CPU 6 PID 1684 [systemd-udevd] May 28 10:24:32 lahna kernel: check_submounts_and_drop[0000:00:14.0/usb3/3-10/3-10.4]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A May 28 10:24:32 lahna kernel: shrink[usb3/3-10/3-10.4/ltm_capable]; CPU 7 PID 1685 [systemd-udevd] May 28 10:24:32 lahna kernel: A This goes on an on with a variable amount of 'A's printed. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
