Bug 47701
| Summary: | When too many disks fall out at the same time, RCU hangs | ||
|---|---|---|---|
| Product: | IO/Storage | Reporter: | Steinar H. Gunderson (steinar+kernel) |
| Component: | SCSI | Assignee: | linux-scsi (linux-scsi) |
| Status: | RESOLVED CODE_FIX | ||
| Severity: | normal | CC: | alan, joe.lawrence, lists2009 |
| Priority: | P1 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | 3.5.4 | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
| Attachments: | dmesg of boot, and removal of one drive at 9462 seconds. | ||
Created attachment 82531 [details]
dmesg of boot, and removal of one drive at 9462 seconds.
I can reproduce this on 3.5.5 & 3.6.
I have 2 of these cards : 01:00.0 Serial Attached SCSI controller: LSI Logic / Symbios Logic SAS2008 PCI-Express Fusion-MPT SAS-2 [Falcon] (rev 02)
My test setup places only 2 drives on the SAS cards. I create a RAID10 from them. Simply pulling a drive will cause the following RCU hang, and prevent the machine from syncing, rebooting or being able to use the array. Alt-sysrq gets me rebooted and back up and running. 100% reproducible.
Stratus noticed a similar crash (hang actually) earlier this week when removing a single SAS disk as part of a RAID 1 MD mirror. In our instance, the all CPUs were idle, except one that was running scsi_target_reap and another waiting on RCU synchronize_sched. Since the former function was stuck in some loop, RCU stalled and the machine wedged. Another Stratus engineer noticed patch [1], and once applied to our kernel, MD/mpt2sas disk removal no longer hung the machine. [1] [SCSI] scsi_remove_target: fix softlockup regression on hot remove https://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=bc3f02a795d3b4faa99d37390174be2a75d091bd Apparently fixed as of 3.6.0-07201-ged5062d (current git as of 8 hours ago). |
Hi, For whatever reason, I lost all of my disks at the same time (I guess a SAS cable fell out; I'll know tomorrow). As was expected, I/O on the machine was not so happy afterwards; what was not so expected, was the following output on the serial console a minute or so after: [292657.601264] INFO: rcu_sched self-detected stall on CPU[292657.602441] INFO: rcu_sched detected stalls on CPUs/tasks: { 6} (detected by 4, t=60002 jiffies) [292657.602444] INFO: Stall ended before state dump start [292657.620982] {[292657.622964] 6} (t=60024 jiffies) Pid: 7800, comm: kworker/u:9 Not tainted 3.5.4 #1 [292657.631337] Call Trace: [292657.634069] <IRQ> [<ffffffff8108ecaf>] __rcu_pending+0xbd/0x417 [292657.640471] [<ffffffff8108f0de>] rcu_check_callbacks+0xd5/0x138 [292657.646765] [<ffffffff81041b73>] update_process_times+0x3c/0x73 [292657.653050] [<ffffffff81072076>] tick_sched_timer+0x6a/0x93 [292657.658999] [<ffffffff8105301e>] __run_hrtimer+0xb3/0x13e [292657.664763] [<ffffffff8107200c>] ? tick_nohz_handler+0xd3/0xd3 [292657.670972] [<ffffffff8103b7a3>] ? __do_softirq+0x16c/0x182 [292657.676916] [<ffffffff810533d5>] hrtimer_interrupt+0xce/0x1b0 [292657.683030] [<ffffffff8101ad3d>] smp_apic_timer_interrupt+0x81/0x94 [292657.689676] [<ffffffff81377447>] apic_timer_interrupt+0x67/0x70 [292657.695965] <EOI> [<ffffffff813703dd>] ? _raw_spin_unlock_irqrestore+0x9/0xb [292657.703695] [<ffffffff8123daaa>] scsi_remove_target+0x137/0x153 [292657.709985] [<ffffffff812425dc>] sas_rphy_remove+0x25/0x4e [292657.715841] [<ffffffff81242616>] sas_rphy_delete+0x11/0x1e [292657.721699] [<ffffffff81242648>] sas_port_delete+0x25/0x11a [292657.727644] [<ffffffff8136de53>] ? mutex_unlock+0x9/0xb [292657.733254] [<ffffffffa0020fd5>] mpt2sas_transport_port_remove+0x16f/0x190 [mpt2sas] [292657.741576] [<ffffffffa001a70b>] _scsih_remove_device+0x58/0x84 [mpt2sas] [292657.748731] [<ffffffffa001a7f4>] _scsih_device_remove_by_handle+0xbd/0xc6 [mpt2sas] [292657.756960] [<ffffffffa001c5bb>] _scsih_sas_topology_change_event+0x422/0x46d [mpt2sas] [292657.765531] [<ffffffff81064556>] ? idle_balance+0xde/0x10c [292657.771395] [<ffffffffa001e098>] ? _scsih_abort+0x1c1/0x1c1 [mpt2sas] [292657.778212] [<ffffffffa001e38d>] _firmware_event_work+0x2f5/0x920 [mpt2sas] [292657.785547] [<ffffffff81042089>] ? add_timer+0x17/0x1a [292657.791058] [<ffffffff8104bc64>] ? queue_delayed_work_on+0xda/0xe8 [292657.797607] [<ffffffffa001e098>] ? _scsih_abort+0x1c1/0x1c1 [mpt2sas] [292657.804418] [<ffffffff8104c641>] process_one_work+0x253/0x3c5 [292657.810534] [<ffffffff8104cbb7>] worker_thread+0x1d4/0x34d [292657.816394] [<ffffffff8104c9e3>] ? rescuer_thread+0x230/0x230 [292657.822511] [<ffffffff810500bb>] kthread+0x84/0x8c [292657.827675] [<ffffffff81377c94>] kernel_thread_helper+0x4/0x10 [292657.833875] [<ffffffff81050037>] ? kthread_freezable_should_stop+0x58/0x58 [292657.841117] [<ffffffff81377c90>] ? gs_change+0xb/0xb I'm reporting this primarily because it could cause problems in some other context (say, when only one or two disks disappear); of course, for me in this case, it wouldn't matter if I/O was "properly" rejected or the entire machine hanged, it's useless anyway.