From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Jones Subject: Re: ext4_es_lookup_extent causing rcu stalls. Date: Thu, 7 May 2015 18:29:21 -0400 Message-ID: <20150507222921.GA11085@codemonkey.org.uk> References: <20150507143552.GA19619@codemonkey.org.uk> <20150507193611.GM5381@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Linux Kernel , linux-ext4@vger.kernel.org To: "Paul E. McKenney" Return-path: Content-Disposition: inline In-Reply-To: <20150507193611.GM5381@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org 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: > > [] sched_show_task+0x165/0x280 > > [] ? sched_show_task+0x82/0x280 > > [] rcu_check_callbacks+0xb26/0xb30 > > [] update_process_times+0x39/0x60 > > [] tick_sched_handle.isra.20+0x25/0x60 > > [] tick_sched_timer+0x41/0x80 > > [] __run_hrtimer+0xba/0x5f0 > > [] ? tick_sched_do_timer+0x40/0x40 > > [] hrtimer_interrupt+0x103/0x230 > > [] ? vtime_common_account_irq_enter+0x32/0x50 > > [] local_apic_timer_interrupt+0x3c/0x70 > > [] smp_apic_timer_interrupt+0x41/0x60 > > [] apic_timer_interrupt+0x70/0x80 > > [] ? lock_acquire+0xd7/0x270 > > [] ? ext4_es_find_delayed_extent_range+0x76/0x480 > > [] _raw_read_lock+0x3b/0x50 > > [] ? ext4_es_find_delayed_extent_range+0x76/0x480 > > [] ext4_es_find_delayed_extent_range+0x76/0x480 > > [] ext4_llseek+0x291/0x410 > > [] ? trace_hardirqs_on+0xd/0x10 > > [] SyS_lseek+0x99/0xc0 > > [] 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: [] sched_show_task+0x165/0x280 [] ? sched_show_task+0x82/0x280 [] dump_cpu_task+0x3d/0x50 [] rcu_dump_cpu_stacks+0x91/0xd0 [] rcu_check_callbacks+0x7ec/0xb30 [] ? tick_do_update_jiffies64+0xde/0x140 [] update_process_times+0x39/0x60 [] tick_sched_handle.isra.20+0x25/0x60 [] tick_sched_timer+0x41/0x80 [] __run_hrtimer+0xba/0x5f0 [] ? tick_sched_do_timer+0x40/0x40 [] hrtimer_interrupt+0x103/0x230 [] ? vtime_common_account_irq_enter+0x32/0x50 [] local_apic_timer_interrupt+0x3c/0x70 [] smp_apic_timer_interrupt+0x41/0x60 [] apic_timer_interrupt+0x70/0x80 [] ? lock_acquire+0xd7/0x270 [] ? ext4_es_lookup_extent+0x5e/0x470 [] _raw_read_lock+0x3b/0x50 [] ? ext4_es_lookup_extent+0x5e/0x470 [] ext4_es_lookup_extent+0x5e/0x470 [] ext4_map_blocks+0x5b/0x590 [] ? ext4_es_find_delayed_extent_range+0x42c/0x480 [] ext4_llseek+0x271/0x410 [] ? trace_hardirqs_on+0xd/0x10 [] SyS_lseek+0x99/0xc0 [] system_call_fastpath+0x12/0x6f