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[104.155.38.26]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e75223ea47sm3592410f8f.46.2025.09.09.12.03.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Sep 2025 12:03:05 -0700 (PDT) Date: Tue, 9 Sep 2025 19:03:01 +0000 From: Mostafa Saleh To: Peter Griffin Cc: linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, krzk@kernel.org, alim.akhtar@samsung.com, =?iso-8859-1?Q?Andr=E9?= Draszik Subject: Re: [PATCH] soc: samsung: exynos-pmu: Fix for CONFIG_DEBUG_PREEMPT Message-ID: References: <20250905162446.88987-1-smostafa@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hi Peter, On Tue, Sep 09, 2025 at 12:14:51PM +0100, Peter Griffin wrote: > Hi Mostafa, > > Thanks for your patch and bug report, it's great to see more folks > running upstream Pixel 6 :) > > On Fri, 5 Sept 2025 at 17:25, 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 > > > > As this value is only read once, it doesn't require to be stable, so > > just use "raw_smp_processor_id" instead. > > Can I ask what baseline you are running when you see this warning? > > As this code got refactored recently in commit 78b72897a5c8 ("soc: > samsung: exynos-pmu: Enable CPU Idle for gs101") which is present in > linux-next but hasn't made its way to a proper release yet. After this > patch smp_processor_id() is always called with a raw_spin_lock() held > (so this warning shouldn't fire). > > I just built next-20250909 locally to confirm, and with the above > patch reverted I see the warning you mention. So in summary I think > the issue has already been fixed by the above commit. I am on commit commit d69eb204c255c35abd9e8cb621484e8074c75eaa Merge: 68f285e26478 9b2bfdbf43ad Author: Linus Torvalds Date: Thu Sep 4 09:59:15 2025 -0700 Merge tag 'net-6.17-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net Which doesn't have the commit you mentioned as it is in the Maintainer's tree, thanks for pointing that. Thanks, Mostafa > > Thanks, > > Peter