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SubjectRe: [PATCH v3] firmware: arm_sdei: Fix sleep from invalid context BUG
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On 2/15/23 19:13, James Morse wrote:
> Hi Pierre, Will,
>
> On 15/02/2023 16:09, Pierre Gondois wrote:
>> Running a preemp_rt kernel based on vv6.2-rc3-rt1 based kernel on an
>> Ampere Altra triggers:
>> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
>> in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 24, name: cpuhp/0
>> preempt_count: 0, expected: 0
>> RCU nest depth: 0, expected: 0
>> 3 locks held by cpuhp/0/24:
>> #0: ffffda30217c70d0 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
>> #1: ffffda30217c7120 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
>> #2: ffffda3021c711f0 (sdei_list_lock){....}-{3:3}, at: sdei_cpuhp_up+0x3c/0x130
>> irq event stamp: 36
>> hardirqs last enabled at (35): [<ffffda301e85b7bc>] finish_task_switch+0xb4/0x2b0
>> hardirqs last disabled at (36): [<ffffda301e812fec>] cpuhp_thread_fun+0x21c/0x248
>> softirqs last enabled at (0): [<ffffda301e80b184>] copy_process+0x63c/0x1ac0
>> softirqs last disabled at (0): [<0000000000000000>] 0x0
>> CPU: 0 PID: 24 Comm: cpuhp/0 Not tainted 5.19.0-rc3-rt5-[...]
>> Hardware name: WIWYNN Mt.Jade Server [...]
>> Call trace:
>> dump_backtrace+0x114/0x120
>> show_stack+0x20/0x70
>> dump_stack_lvl+0x9c/0xd8
>> dump_stack+0x18/0x34
>> __might_resched+0x188/0x228
>> rt_spin_lock+0x70/0x120
>> sdei_cpuhp_up+0x3c/0x130
>> cpuhp_invoke_callback+0x250/0xf08
>> cpuhp_thread_fun+0x120/0x248
>> smpboot_thread_fn+0x280/0x320
>> kthread+0x130/0x140
>> ret_from_fork+0x10/0x20
>>
>> sdei_cpuhp_up() is called in the STARTING hotplug section,
>> which runs whith interrupts disabled. Use a CPUHP_AP_ONLINE_DYN entry
>
> Typo: with
>
>> instead to execute the cpuhp cb later, with preemption enabled.
>>
>> SDEI originaly got its own cpuhp slot because to allow interracting
>
> Typo: originally
> Typo: interacting
>
>> with perf. It got superseded by pNMI and this early slot is not
>> relevant anymore. [1]
>
> (Please add a spell checker to your workflow. 'codespell' knows which bits of
> a diff it should check)
>
> "because to allow interacting" isn't easy to parse, "to allow an interaction with"?
>
>
>> Some SDEI calls (e.g. SDEI_1_0_FN_SDEI_PE_MASK) take actions on the
>> calling CPU. It is checked that preemption is disabled for them.
>> _ONLINE cpuhp cb are executed in the 'per CPU hotplug thread'.
>> Preemption is enabled in those threads, but their cpumask is limited
>> to 1 CPU.
>> Move 'WARN_ON_ONCE(preemptible())' statements so that SDEI cpuhp cb
>> don't trigger them.
>>
>> Also add a check for the SDEI_1_0_FN_SDEI_PRIVATE_RESET SDEI call
>> which acts on the calling CPU.
>
> Thanks for sticking with this,
>
> Reviewed-by: James Morse <james.morse@arm.com>
>
>
> Will, are you happy to pick this up and fix the typos, or would you prefer a clean version
> to be posted?

I re-posted the patch with the typos corrected at:
https://lore.kernel.org/all/20230216084920.144064-1-pierre.gondois@arm.com/

sorry for those,
Regards,
Pierre

>
>
> Thanks,
>
> James

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