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From: Valentin Schneider <valentin.schneider@arm.com>
To: Guenter Roeck <linux@roeck-us.net>, linux-kernel@vger.kernel.org
Cc: linux-tip-commits@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	x86@kernel.org
Subject: Re: [tip: sched/core] sched/core: Initialize the idle task with preemption disabled
Date: Wed, 07 Jul 2021 00:55:20 +0100	[thread overview]
Message-ID: <87fswr6lqv.mognet@arm.com> (raw)
In-Reply-To: <20210706194456.GA1823793@roeck-us.net>


Hi Guenter,

On 06/07/21 12:44, Guenter Roeck wrote:
> This patch results in several messages similar to the following
> when booting s390 images in qemu.
>
> [    1.690807] BUG: sleeping function called from invalid context at include/linux/percpu-rwsem.h:49
> [    1.690925] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0
> [    1.691053] no locks held by swapper/0/1.
> [    1.691310] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-11788-g79160a603bdb #1
> [    1.691469] Hardware name: QEMU 2964 QEMU (KVM/Linux)
> [    1.691612] Call Trace:
> [    1.691718]  [<0000000000d98bb0>] show_stack+0x90/0xf8
> [    1.692040]  [<0000000000da894c>] dump_stack_lvl+0x74/0xa8
> [    1.692134]  [<0000000000187e52>] ___might_sleep+0x15a/0x170
> [    1.692228]  [<000000000014f588>] cpus_read_lock+0x38/0xc0
> [    1.692320]  [<0000000000182e8a>] smpboot_register_percpu_thread+0x2a/0x160
> [    1.692412]  [<00000000014814b8>] cpuhp_threads_init+0x28/0x60
> [    1.692505]  [<0000000001487a30>] smp_init+0x28/0x90
> [    1.692597]  [<00000000014779a6>] kernel_init_freeable+0x1f6/0x270
> [    1.692689]  [<0000000000db7466>] kernel_init+0x2e/0x160
> [    1.692779]  [<0000000000103618>] __ret_from_fork+0x40/0x58
> [    1.692870]  [<0000000000dc6e12>] ret_from_fork+0xa/0x30
>
> Reverting this patch fixes the problem.
> Bisect log is attached.
>
> Guenter
>

Thanks for the report.

So somehow the init task ends up with a non-zero preempt_count()? Per
FORK_PREEMPT_COUNT we should exit __ret_from_fork() with a zero count, are
you hitting the WARN_ONCE() in finish_task_switch()?

Does CONFIG_DEBUG_PREEMPT=y yield anything interesting?

I can't make sense of this right now, but it's a bit late :) I'll grab some
toolchain+qemu tomorrow and go poke at it (and while at it I need to do the
same with powerpc).

  reply	other threads:[~2021-07-06 23:55 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-12  9:46 [PATCH] sched: Initialize the idle task with preemption disabled Valentin Schneider
2021-05-12 11:15 ` [tip: sched/core] sched/core: " tip-bot2 for Valentin Schneider
2021-07-06 19:44   ` Guenter Roeck
2021-07-06 23:55     ` Valentin Schneider [this message]
2021-07-07  4:06       ` Guenter Roeck
2021-07-07 12:03       ` Frederic Weisbecker
2021-07-07 12:11         ` Valentin Schneider
2021-07-07 14:14           ` Guenter Roeck
2021-07-07 14:35             ` Alexey Kardashevskiy
2021-07-07 14:57               ` Valentin Schneider
2021-07-07 15:31                 ` Guenter Roeck
2021-07-07 16:35                 ` Guenter Roeck
2021-07-07 17:31                   ` Valentin Schneider
2021-07-08  1:50                     ` Alexey Kardashevskiy

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