linux-kernel - Re: [PATCH v2] powerpc/smp: do not decrement idle task preempt count in CPU offline

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Message-Id: <163481445875.3437586.10466955312828450807.b4-ty@ellerman.id.au>
Date:   Thu, 21 Oct 2021 22:07:38 +1100
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Nathan Lynch <nathanl@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org
Cc:     mpe@...erman.id.au, clg@...d.org, linux-kernel@...r.kernel.org,
        valentin.schneider@....com, srikar@...ux.vnet.ibm.com,
        peterz@...radead.org, mingo@...nel.org
Subject: Re: [PATCH v2] powerpc/smp: do not decrement idle task preempt count in CPU offline

On Fri, 15 Oct 2021 12:39:02 -0500, Nathan Lynch wrote:
> With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we
> get:
> 
> BUG: scheduling while atomic: swapper/1/0/0x00000000
> no locks held by swapper/1/0.
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100
> Call Trace:
>  dump_stack_lvl+0xac/0x108
>  __schedule_bug+0xac/0xe0
>  __schedule+0xcf8/0x10d0
>  schedule_idle+0x3c/0x70
>  do_idle+0x2d8/0x4a0
>  cpu_startup_entry+0x38/0x40
>  start_secondary+0x2ec/0x3a0
>  start_secondary_prolog+0x10/0x14
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/smp: do not decrement idle task preempt count in CPU offline
      https://git.kernel.org/powerpc/c/787252a10d9422f3058df9a4821f389e5326c440

cheers