Re: rcu self-detected stall messages on OMAP3, 4 boards

[Paul Walmsley]

Hi Paul

On Fri, 21 Sep 2012, Paul E. McKenney wrote:

> I am wondering if your system somehow figured out how to start a grace
> period that had no RCU callbacks waiting for it.  If that happened,
> then a CONFIG_NO_HZ=y system could in theory get into a state where all
> CPUs are in dyntick-idle mode, so that none of them is doing anything
> to force the grace period to complete.
>
> That should be easy to diagnose, anyway.  Please see below, which
> includes the earlier diagnostic patch.

Here you go.
 
- Paul

[  248.902618] INFO: rcu_sched self-detected stall on CPU
[  248.905456]  0: (1 ticks this GP) idle=933/1/0 
[  248.907897]   (t=26570 jiffies g=11 c=10 q=0)
[  248.910339] [<c001bc90>] (unwind_backtrace+0x0/0xf0) from [<c00ad800>] (rcu_check_callbacks+0x220/0x714)
[  248.915527] [<c00ad800>] (rcu_check_callbacks+0x220/0x714) from [<c00532a0>] (update_process_times+0x38/0x68)
[  248.920928] [<c00532a0>] (update_process_times+0x38/0x68) from [<c008c9e8>] (tick_sched_timer+0x80/0xec)
[  248.926116] [<c008c9e8>] (tick_sched_timer+0x80/0xec) from [<c0068ed4>] (__run_hrtimer+0x7c/0x1e0)
[  248.930999] [<c0068ed4>] (__run_hrtimer+0x7c/0x1e0) from [<c0069cb8>] (hrtimer_interrupt+0x11c/0x2d0)
[  248.936035] [<c0069cb8>] (hrtimer_interrupt+0x11c/0x2d0) from [<c001a3cc>] (twd_handler+0x30/0x44)
[  248.940948] [<c001a3cc>] (twd_handler+0x30/0x44) from [<c00a7bd0>] (handle_percpu_devid_irq+0x90/0x13c)
[  248.946075] [<c00a7bd0>] (handle_percpu_devid_irq+0x90/0x13c) from [<c00a4344>] (generic_handle_irq+0x30/0x48)
[  248.951538] [<c00a4344>] (generic_handle_irq+0x30/0x48) from [<c0014e38>] (handle_IRQ+0x4c/0xac)
[  248.956329] [<c0014e38>] (handle_IRQ+0x4c/0xac) from [<c00084cc>] (gic_handle_irq+0x28/0x5c)
[  248.960937] [<c00084cc>] (gic_handle_irq+0x28/0x5c) from [<c04fb1a4>] (__irq_svc+0x44/0x5c)
[  248.965484] Exception stack(0xc0729f58 to 0xc0729fa0)
[  248.968231] 9f40:                                                       0003b832 00000001
[  248.972686] 9f60: 00000000 c074a8e8 c0728000 c07c42c8 c05065a0 c074bdc8 00000000 411fc092
[  248.977142] 9f80: c074bfe8 00000000 00000001 c0729fa0 0003b833 c0015130 20000113 ffffffff
[  248.981597] [<c04fb1a4>] (__irq_svc+0x44/0x5c) from [<c0015130>] (default_idle+0x20/0x44)
[  248.986083] [<c0015130>] (default_idle+0x20/0x44) from [<c001535c>] (cpu_idle+0x9c/0x114)
[  248.990539] [<c001535c>] (cpu_idle+0x9c/0x114) from [<c06d77b0>] (start_kernel+0x2b4/0x304)
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