linux-kernel - Re: [rfc patch v4.4-rt2] sched: fix up preempt lazy forward port

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Message-ID: <56A22FE7.6070005@ti.com>
Date:	Fri, 22 Jan 2016 15:34:31 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Mike Galbraith <umgwanakikbuti@...il.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: Re: [rfc patch v4.4-rt2] sched: fix up preempt lazy forward port

On 01/22/2016 03:19 PM, Sebastian Andrzej Siewior wrote:
> On 01/22/2016 01:24 PM, Grygorii Strashko wrote:
>> I can see below backtrace during boot if i backport this change in K4.1-rt
>> TI am437x-idk (UP) board.
>>
>> [    0.204022] Switched to clocksource arm_global_timer
>> [    0.211982] ------------[ cut here ]------------
>> [    0.212021] WARNING: CPU: 0 PID: 3 at kernel/softirq.c:894 __tasklet_action+0x150/0x17c()
>> [    0.212027] Modules linked in:
>> [    0.212041] CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.1.15-rt11-00324-g52f8148-dirty #117
>> [    0.212046] Hardware name: Generic AM43 (Flattened Device Tree)
>> [    0.212052] Backtrace:
>> [    0.212080] [<c0012b50>] (dump_backtrace) from [<c0012d70>] (show_stack+0x18/0x1c)
>> [    0.212085]  r7:c0730a84 r6:0000037e r5:00000009 r4:00000000
>> [    0.212112] [<c0012d58>] (show_stack) from [<c05e6940>] (dump_stack+0x20/0x28)
>> [    0.212124] [<c05e6920>] (dump_stack) from [<c003713c>] (warn_slowpath_common+0x7c/0xb4)
>> [    0.212134] [<c00370c0>] (warn_slowpath_common) from [<c0037218>] (warn_slowpath_null+0x24/0x2c)
>> [    0.212138]  r8:000f4240 r7:00000000 r6:c0841238 r5:00000018 r4:00000006
>> [    0.212156] [<c00371f4>] (warn_slowpath_null) from [<c003a0a4>] (__tasklet_action+0x150/0x17c)
>> [    0.212165] [<c0039f54>] (__tasklet_action) from [<c003a138>] (tasklet_action+0x30/0x38)
>> [    0.212169]  r9:04208140 r8:c0862300 r7:000000c0 r6:c082d774 r5:00000018 r4:00000006
>> [    0.212187] [<c003a108>] (tasklet_action) from [<c0039c2c>] (do_current_softirqs+0x190/0x258)
>> [    0.212197] [<c0039a9c>] (do_current_softirqs) from [<c003a170>] (run_ksoftirqd+0x30/0x58)
>> [    0.212201]  r10:00000000 r9:00000000 r8:00000002 r7:c082d8f0 r6:00000001 r5:ee81f740
>> [    0.212213]  r4:ee874000
>> [    0.212227] [<c003a140>] (run_ksoftirqd) from [<c00534e0>] (smpboot_thread_fn+0x15c/0x278)
>> [    0.212242] [<c0053384>] (smpboot_thread_fn) from [<c00500fc>] (kthread+0xcc/0xe4)
>> [    0.212246]  r9:00000000 r8:00000000 r7:c0053384 r6:ee81f740 r5:ee81f780 r4:00000000
>> [    0.212265] [<c0050030>] (kthread) from [<c000f988>] (ret_from_fork+0x14/0x2c)
>> [    0.212269]  r7:00000000 r6:00000000 r5:c0050030 r4:ee81f780
>> [    0.212279] ---[ end trace 0000000000000001 ]---
>> [    0.212284] softirq: ================== c037d4c4 <---- t->func
>> ^^
>> # grep c037d4c4 System.map
>> c037d4c4 t kbd_bh
>
> Do you still see it with the missing lazy bits? I don't see where this
> could come from.
>

yep. I've tried it with and without changing _TIF_WORK_MASK
Seems It's triggered by Virtual terminal keyboard_tasklet

-- 
regards,
-grygorii