Re: [PATCH v3] firmware: arm_sdei: Fix sleep from invalid context BUG

[Pierre Gondois]

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 It got superseded by pNMI and this early slot is not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@xxxxxxx>
>
>
> 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@xxxxxxx/

sorry for those,
Regards,
Pierre

> Thanks,
>
> James