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Message-ID: <19a6f296-eb40-49cf-9571-2d7964cd3313@kernel.org>
Date: Fri, 5 Sep 2025 19:09:09 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Mostafa Saleh <smostafa@...gle.com>,
linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: alim.akhtar@...sung.com, Peter Griffin <peter.griffin@...aro.org>,
André Draszik <andre.draszik@...aro.org>
Subject: Re: [PATCH] soc: samsung: exynos-pmu: Fix for CONFIG_DEBUG_PREEMPT
On 05/09/2025 18:24, Mostafa Saleh wrote:
> Booting the kernel on Pixel-6 with `CONFIG_DEBUG_PREEMPT` prints the
> following WARN:
>
> [ 0.784187][ T1] BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
> [ 0.784328][ T1] caller is debug_smp_processor_id+0x20/0x30
> [ 0.784433][ T1] CPU: 6 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.17.0-rc4-gd69eb204c255 #1 PREEMPT
> [ 0.784439][ T1] Hardware name: Oriole (DT)
> [ 0.784441][ T1] Call trace:
> [ 0.784443][ T1] show_stack+0x34/0xa0 (C)
> [ 0.784453][ T1] dump_stack_lvl+0x7c/0xb0
> [ 0.784460][ T1] dump_stack+0x18/0x24
> [ 0.784464][ T1] check_preemption_disabled+0xf8/0x100
> [ 0.784470][ T1] debug_smp_processor_id+0x20/0x30
> [ 0.784476][ T1] gs101_cpuhp_pmu_online+0x40/0x108
> [ 0.784483][ T1] cpuhp_invoke_callback+0x188/0x2d8
> [ 0.784490][ T1] cpuhp_issue_call+0xec/0x240
> [ 0.784494][ T1] __cpuhp_setup_state_cpuslocked+0x140/0x2c0
> [ 0.784499][ T1] __cpuhp_setup_state+0x58/0x88
> [ 0.784504][ T1] exynos_pmu_probe+0x2a4/0x380
> [ 0.784508][ T1] platform_probe+0x64/0xd0
> [ 0.784516][ T1] really_probe+0xd0/0x3b0
> [ 0.784520][ T1] __driver_probe_device+0x8c/0x170
> [ 0.784524][ T1] driver_probe_device+0x44/0x140
> [ 0.784528][ T1] __device_attach_driver+0xd8/0x180
> [ 0.784532][ T1] bus_for_each_drv+0x90/0xf8
> [ 0.784536][ T1] __device_attach+0xa8/0x1d0
> [ 0.784540][ T1] device_initial_probe+0x1c/0x30
> [ 0.784544][ T1] bus_probe_device+0xb4/0xc0
> [ 0.784547][ T1] device_add+0x4d0/0x700
> [ 0.784550][ T1] of_device_add+0x4c/0x78
> [ 0.784556][ T1] of_platform_device_create_pdata+0x9c/0x148
> [ 0.784560][ T1] of_platform_bus_create+0x1d0/0x370
> [ 0.784563][ T1] of_platform_bus_create+0x234/0x370
> [ 0.784567][ T1] of_platform_populate+0x84/0x178
> [ 0.784571][ T1] of_platform_default_populate_init+0xf0/0x120
> [ 0.784579][ T1] do_one_initcall+0x68/0x2d0
> [ 0.784585][ T1] kernel_init_freeable+0x2d8/0x358
> [ 0.784589][ T1] kernel_init+0x28/0x168
> [ 0.784595][ T1] ret_from_fork+0x10/0x20
Please trim from unnecessary parts - [time].
>
> As this value is only read once, it doesn't require to be stable, so
Why it does not need to be stable? Onlining wrong CPU number is not
desired...
> just use "raw_smp_processor_id" instead.
You might be just hiding some other real issue, because above stacktrace
is from gs101_cpuhp_pmu_online() which IRQs disabled and preemption
disabled. Provide analysis of the warning, instead of just making it
disappear.
>
> Cc: Peter Griffin <peter.griffin@...aro.org>
> Cc: André Draszik <andre.draszik@...aro.org>
>
No blank lines between tags.
Missing Fixes tag... and then Cc is not necessary. Please follow
standard kernel process.
> Signed-off-by: Mostafa Saleh <smostafa@...gle.com>
> ---
> drivers/soc/samsung/exynos-pmu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/soc/samsung/exynos-pmu.c b/drivers/soc/samsung/exynos-pmu.c
> index a77288f49d24..338f4758a089 100644
> --- a/drivers/soc/samsung/exynos-pmu.c
> +++ b/drivers/soc/samsung/exynos-pmu.c
> @@ -338,7 +338,7 @@ EXPORT_SYMBOL_GPL(exynos_get_pmu_regmap_by_phandle);
>
Best regards,
Krzysztof
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