Date:	Mon, 30 Nov 2015 10:28:54 +0000
From:	Fabrice Triboix <fabrice.triboix@...ova.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [SCHED] rcu_sched kthread starved for N jiffies! + stack trace

Dear All,

I did some soak testing of our application (running on linux) over the weekend. Our application runs on a dedicated linux system.
This morning, I saw in "/var/log/message" the following message repeated 70 times "rcu_sched kthread starved for N jiffies!" (N being a number in the tens of thousands). It also comes with a stack trace. Please find a copy/paste of the latest error message below.

For information, we are using SCHED_FIFO for some threads that needs to run with very low-latency (video card captures).

If anyone could shed some light on what that means, that would be greatly appreciated!

Many thanks,

  Fabrice Triboix


    ftenc:~# grep kernel /var/log/messages | tail -30
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369148]  [<ffffffff81887e0f>] apic_timer_interrupt+0x6f/0x80
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369149]  <EOI>  [<ffffffff81887b42>] ? retint_restore_args+0xe/0xe
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369154]  [<ffffffff8100cae5>] ? default_idle+0x25/0xb0
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369156]  [<ffffffff8100cae3>] ? default_idle+0x23/0xb0
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369158]  [<ffffffff8100d42f>] arch_cpu_idle+0xf/0x20
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369162]  [<ffffffff810f64a5>] cpu_startup_entry+0x2e5/0x400
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369164]  [<ffffffff81127103>] ? clockevents_register_device+0xe3/0x140
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369167]  [<ffffffff8112718c>] ? clockevents_config_and_register+0x2c/0x40
    Nov 30 09:13:33 plink-buildroot user.warn kernel: [332879.369169]  [<ffffffff8103448a>] start_secondary+0x13a/0x150
    Nov 30 09:13:33 plink-buildroot user.err kernel: [332879.369171] rcu_sched kthread starved for 20999 jiffies!
    Nov 30 09:32:14 plink-buildroot user.err kernel: [334000.974890] INFO: rcu_sched detected stalls on CPUs/tasks: {} (detected by 5, t=21002 jiffies, g=6612437, c=6612436, q=11267)
    Nov 30 09:32:14 plink-buildroot user.err kernel: [334000.974900] All QSes seen, last rcu_sched kthread activity 20999 (4628342351-4628321352), jiffies_till_next_fqs=3
    Nov 30 09:32:14 plink-buildroot user.info kernel: [334000.974903] mux-0           R  running task        0 10129   8797 0x00000000
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974907]  ffffffff81e4c3c0 ffff88089fc83dd8 ffffffff810e53ef ffff88089fc943c0
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974909]  ffffffff81e4c3c0 ffff88089fc83e48 ffffffff811157cc ffff880837edbf00
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974911]  ffff88089fc943c0 0000000000002c03 000000000064e5d5 0000000000000000
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974914] Call Trace:
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974916]  <IRQ>  [<ffffffff810e53ef>] sched_show_task+0xaf/0x120
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974934]  [<ffffffff811157cc>] rcu_check_callbacks+0x70c/0x780
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974937]  [<ffffffff8111a5e9>] update_process_times+0x39/0x60
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974942]  [<ffffffff811296f6>] tick_sched_handle.isra.16+0x36/0x50
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974945]  [<ffffffff81129754>] tick_sched_timer+0x44/0x80
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974947]  [<ffffffff8111b2f0>] __run_hrtimer+0x80/0x1c0
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974950]  [<ffffffff81129710>] ? tick_sched_handle.isra.16+0x50/0x50
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974952]  [<ffffffff8111b693>] hrtimer_interrupt+0xf3/0x210
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974958]  [<ffffffff81035c99>] local_apic_timer_interrupt+0x39/0x60
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974964]  [<ffffffff81889a25>] smp_apic_timer_interrupt+0x45/0x60
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974967]  [<ffffffff81887e0f>] apic_timer_interrupt+0x6f/0x80
    Nov 30 09:32:14 plink-buildroot user.warn kernel: [334000.974968]  <EOI>  [<ffffffff81887abe>] ? retint_swapgs+0xe/0x44
    Nov 30 09:32:14 plink-buildroot user.err kernel: [334000.974971] rcu_sched kthread starved for 20999 jiffies!
    ftenc:~#
    ftenc:~#
    ftenc:~# uname -a
    Linux plink-buildroot 4.0.0 #2 SMP Thu Nov 26 10:34:48 GMT 2015 x86_64 GNU/Linux



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