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Date: Fri, 8 May 2015 09:02:01 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Dave Jones <davej@...emonkey.org.uk>, Linux Kernel <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org Subject: Re: ext4_es_lookup_extent causing rcu stalls. On Thu, May 07, 2015 at 06:29:21PM -0400, Dave Jones wrote: > Content analysis details: (-2.9 points, 5.0 required) > > pts rule name description > ---- ---------------------- -------------------------------------------------- > -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP > -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% > [score: 0.0000] > X-Authenticated-User: davej@...emonkey.org.uk > X-ZLA-Header: unknown; 0 > X-ZLA-DetailInfo: BA=6.00003273; NDR=6.00000001; ZLA=6.00000002; ZF=6.00000004; ZB=6.00039413; ZH=6.00098335; ZP=6.00077780; ZU=6.00000001; UDB=6.00219514; UTC=2015-05-07 22:29:31 > x-cbid: 15050722-0037-0000-0000-000001281E1A > X-IBM-ISS-SpamDetectors: Score=0.40962; BY=0.04766; FL=0; FP=0; FZ=0; HX=0; > KW=0; PH=0; RB=0; SC=0.40962; ST=0; TS=0; UL=0; ISC= > X-IBM-ISS-DetailInfo: BY=3.00003915; HX=3.00000235; KW=3.00000007; > PH=3.00000003; SC=3.00000078; SDB=6.00527008; UDB=6.00219514; UTC=2015-05-07 > 22:29:32 > X-TM-AS-MML: disable > > On Thu, May 07, 2015 at 12:36:11PM -0700, Paul E. McKenney wrote: > > > > INFO: rcu_sched detected stalls on CPUs/tasks: > > > (detected by 0, t=6502 jiffies, g=75215, c=75214, q=0) > > > All QSes seen, last rcu_sched kthread activity 6502 (4295121467-4295114965), jiffies_till_next_fqs=1, root ->qsmask 0x0 > > > trinity-c21 R running task 12768 20468 30399 0x0008000c > > > 00000000000031e0 00000000f34c833f ffff88043d803da8 ffffffffb30abd15 > > > ffffffffb30abc32 ffffffffb3c3b500 0000000000001966 ffff88043d817580 > > > ffffffffb3c3b080 0000000000000000 ffff88043d803e28 ffffffffb30ef556 > > > Call Trace: > > > <IRQ> [<ffffffffb30abd15>] sched_show_task+0x165/0x280 > > > [<ffffffffb30abc32>] ? sched_show_task+0x82/0x280 > > > [<ffffffffb30ef556>] rcu_check_callbacks+0xb26/0xb30 > > > [<ffffffffb30f5389>] update_process_times+0x39/0x60 > > > [<ffffffffb3107ef5>] tick_sched_handle.isra.20+0x25/0x60 > > > [<ffffffffb3108191>] tick_sched_timer+0x41/0x80 > > > [<ffffffffb30f643a>] __run_hrtimer+0xba/0x5f0 > > > [<ffffffffb3108150>] ? tick_sched_do_timer+0x40/0x40 > > > [<ffffffffb30f6e93>] hrtimer_interrupt+0x103/0x230 > > > [<ffffffffb30b10e2>] ? vtime_common_account_irq_enter+0x32/0x50 > > > [<ffffffffb3034fec>] local_apic_timer_interrupt+0x3c/0x70 > > > [<ffffffffb372bf51>] smp_apic_timer_interrupt+0x41/0x60 > > > [<ffffffffb372a980>] apic_timer_interrupt+0x70/0x80 > > > <EOI> [<ffffffffb30cde67>] ? lock_acquire+0xd7/0x270 > > > [<ffffffffb329e466>] ? ext4_es_find_delayed_extent_range+0x76/0x480 > > > [<ffffffffb372949b>] _raw_read_lock+0x3b/0x50 > > > [<ffffffffb329e466>] ? ext4_es_find_delayed_extent_range+0x76/0x480 > > > [<ffffffffb329e466>] ext4_es_find_delayed_extent_range+0x76/0x480 > > > [<ffffffffb324f291>] ext4_llseek+0x291/0x410 > > > [<ffffffffb30cb0fd>] ? trace_hardirqs_on+0xd/0x10 > > > [<ffffffffb31cd339>] SyS_lseek+0x99/0xc0 > > > [<ffffffffb3729b97>] system_call_fastpath+0x12/0x6f > > > rcu_sched kthread starved for 6502 jiffies! > > > > If you don't let RCU's grace-period kthreads run, they aren't going to > > be able to help you much. Could you please try building with > > CONFIG_RCU_KTHREAD_PRIO=5 (say) and see if that helps? > > Nope. Though the message is slightly different. > > > INFO: rcu_sched self-detected stall on CPU > 1: (6499 ticks this GP) idle=5ed/140000000000001/0 softirq=6071/6071 fqs=6495 > (t=6500 jiffies g=17107 c=17106 q=0) > Task dump for CPU 1: > trinity-c6 R running task 12576 26108 548 0x0008000c > 0000000000003120 00000000aa7d3446 ffff88043d843d58 ffffffff8e0acb55 > ffffffff8e0aca72 0000000000000001 0000000000000000 0000000000000001 > ffffffff8ec3b0c0 0000000000000082 ffff88043d843d78 ffffffff8e0b090d > Call Trace: > <IRQ> [<ffffffff8e0acb55>] sched_show_task+0x165/0x280 > [<ffffffff8e0aca72>] ? sched_show_task+0x82/0x280 > [<ffffffff8e0b090d>] dump_cpu_task+0x3d/0x50 > [<ffffffff8e0e4971>] rcu_dump_cpu_stacks+0x91/0xd0 > [<ffffffff8e0f009c>] rcu_check_callbacks+0x7ec/0xb30 > [<ffffffff8e10908e>] ? tick_do_update_jiffies64+0xde/0x140 > [<ffffffff8e0f6299>] update_process_times+0x39/0x60 > [<ffffffff8e108ed5>] tick_sched_handle.isra.20+0x25/0x60 > [<ffffffff8e109171>] tick_sched_timer+0x41/0x80 > [<ffffffff8e0f735a>] __run_hrtimer+0xba/0x5f0 > [<ffffffff8e109130>] ? tick_sched_do_timer+0x40/0x40 > [<ffffffff8e0f7db3>] hrtimer_interrupt+0x103/0x230 > [<ffffffff8e0b1f42>] ? vtime_common_account_irq_enter+0x32/0x50 > [<ffffffff8e0355dc>] local_apic_timer_interrupt+0x3c/0x70 > [<ffffffff8e733251>] smp_apic_timer_interrupt+0x41/0x60 > [<ffffffff8e731c80>] apic_timer_interrupt+0x70/0x80 > <EOI> [<ffffffff8e0cecc7>] ? lock_acquire+0xd7/0x270 > [<ffffffff8e2a206e>] ? ext4_es_lookup_extent+0x5e/0x470 > [<ffffffff8e73079b>] _raw_read_lock+0x3b/0x50 > [<ffffffff8e2a206e>] ? ext4_es_lookup_extent+0x5e/0x470 > [<ffffffff8e2a206e>] ext4_es_lookup_extent+0x5e/0x470 > [<ffffffff8e25927b>] ext4_map_blocks+0x5b/0x590 > [<ffffffff8e2a1a4c>] ? ext4_es_find_delayed_extent_range+0x42c/0x480 > [<ffffffff8e252301>] ext4_llseek+0x271/0x410 > [<ffffffff8e0cbf5d>] ? trace_hardirqs_on+0xd/0x10 > [<ffffffff8e1cf479>] SyS_lseek+0x99/0xc0 > [<ffffffff8e730e97>] system_call_fastpath+0x12/0x6f OK, then I am going to guess either extreme lock contention or failure to release the lock. If you are running CONFIG_PROVE_LOCKING, that would indicate contention rather than failure to release the lock. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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