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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82379bfcab8sm299991b3a.36.2026.01.27.11.07.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Jan 2026 11:07:06 -0800 (PST) Sender: Guenter Roeck Message-ID: <402e0322-bc2d-441f-8969-fc643dfaff06@roeck-us.net> Date: Tue, 27 Jan 2026 11:07:05 -0800 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND][PATCH 3/5] perf: Use current->flags & PF_KTHREAD|PF_USER_WORKER instead of current->mm == NULL To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Thomas Gleixner References: <20250820180338.701352023@kernel.org> <20250820180428.592367294@kernel.org> <0d877e6f-41a7-4724-875d-0b0a27b8a545@roeck-us.net> <20260126120553.2fa79048@gandalf.local.home> <20260126121803.4a90c959@gandalf.local.home> <27f9a957-67c7-4c88-b320-0f8725e9b03d@roeck-us.net> <20260127102234.755d8c4e@gandalf.local.home> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAmgrMyQFCSbODQkACgkQyx8mb86fmYGcWRAA oRwrk7V8fULqnGGpBIjp7pvR187Yzx+lhMGUHuM5H56TFEqeVwCMLWB2x1YRolYbY4MEFlQg VUFcfeW0OknSr1s6wtrtQm0gdkolM8OcCL9ptTHOg1mmXa4YpW8QJiL0AVtbpE9BroeWGl9v 2TGILPm9mVp+GmMQgkNeCS7Jonq5f5pDUGumAMguWzMFEg+Imt9wr2YA7aGen7KPSqJeQPpj onPKhu7O/KJKkuC50ylxizHzmGx+IUSmOZxN950pZUFvVZH9CwhAAl+NYUtcF5ry/uSYG2U7 DCvpzqOryJRemKN63qt1bjF6cltsXwxjKOw6CvdjJYA3n6xCWLuJ6yk6CAy1Ukh545NhgBAs rGGVkl6TUBi0ixL3EF3RWLa9IMDcHN32r7OBhw6vbul8HqyTFZWY2ksTvlTl+qG3zV6AJuzT WdXmbcKN+TdhO5XlxVlbZoCm7ViBj1+PvIFQZCnLAhqSd/DJlhaq8fFXx1dCUPgQDcD+wo65 qulV/NijfU8bzFfEPgYP/3LP+BSAyFs33y/mdP8kbMxSCjnLEhimQMrSSo/To1Gxp5C97fw5 3m1CaMILGKCmfI1B8iA8zd8ib7t1Rg0qCwcAnvsM36SkrID32GfFbv873bNskJCHAISK3Xkz qo7IYZmjk/IJGbsiGzxUhvicwkgKE9r7a1rOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAmgrMyQFCSbODQkACgkQyx8mb86fmYHlgg/9 H5JeDmB4jsreE9Bn621wZk7NMzxy9STxiVKSh8Mq4pb+IDu1RU2iLyetCY1TiJlcxnE362kj njrfAdqyPteHM+LU59NtEbGwrfcXdQoh4XdMuPA5ADetPLma3YiRa3VsVkLwpnR7ilgwQw6u dycEaOxQ7LUXCs0JaGVVP25Z2hMkHBwx6BlW6EZLNgzGI2rswSZ7SKcsBd1IRHVf0miwIFYy j/UEfAFNW+tbtKPNn3xZTLs3quQN7GdYLh+J0XxITpBZaFOpwEKV+VS36pSLnNl0T5wm0E/y scPJ0OVY7ly5Vm1nnoH4licaU5Y1nSkFR/j2douI5P7Cj687WuNMC6CcFd6j72kRfxklOqXw zvy+2NEcXyziiLXp84130yxAKXfluax9sZhhrhKT6VrD45S6N3HxJpXQ/RY/EX35neH2/F7B RgSloce2+zWfpELyS1qRkCUTt1tlGV2p+y2BPfXzrHn2vxvbhEn1QpQ6t+85FKN8YEhJEygJ F0WaMvQMNrk9UAUziVcUkLU52NS9SXqpVg8vgrO0JKx97IXFPcNh0DWsSj/0Y8HO/RDkGXYn FDMj7fZSPKyPQPmEHg+W/KzxSSfdgWIHF2QaQ0b2q1wOSec4Rti52ohmNSY+KNIW/zODhugJ np3900V20aS7eD9K8GTU0TGC1pyz6IVJwIE= In-Reply-To: <20260127102234.755d8c4e@gandalf.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Steven, On 1/27/26 07:22, Steven Rostedt wrote: > On Mon, 26 Jan 2026 17:32:35 -0800 > Guenter Roeck wrote: > >> Still crashing, though not as often and with a slightly different backtrace. >> I added the backtrace to the bug report @ Google. > > I figured there would be other locations. A while ago I had a patch to wrap > the checks in a "is_user_thread()" helper function[1], but Ingo had issues > with it. It seems now it's biting us in the butt and let's see if it would > help now. I modified it slightly. > > [1] https://lore.kernel.org/linux-trace-kernel/20250425204313.616425861@goodmis.org/ > > If the below fixes it, I'll resend it, but now as a real bug fix. > Trying. So far I can no longer reproduce the problem with the patch below applied. Obviously that doesn't mean that the problem is fixed, only that I can no longer reproduce it. I'll keep trying with different platforms. Guenter > -- Steve > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index da0133524d08..5f00b5ed0f3b 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1776,6 +1776,11 @@ static __always_inline bool is_percpu_thread(void) > (current->nr_cpus_allowed == 1); > } > > +static __always_inline bool is_user_task(struct task_struct *task) > +{ > + return task->mm && !(task->flags & (PF_KTHREAD | PF_USER_WORKER)); > +} > + > /* Per-process atomic flags. */ > #define PFA_NO_NEW_PRIVS 0 /* May not gain new privileges. */ > #define PFA_SPREAD_PAGE 1 /* Spread page cache over cpuset */ > diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c > index 1f6589578703..9d24b6e0c91f 100644 > --- a/kernel/events/callchain.c > +++ b/kernel/events/callchain.c > @@ -246,7 +246,7 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, > > if (user && !crosstask) { > if (!user_mode(regs)) { > - if (current->flags & (PF_KTHREAD | PF_USER_WORKER)) > + if (!is_user_task(current)) > goto exit_put; > regs = task_pt_regs(current); > } > diff --git a/kernel/events/core.c b/kernel/events/core.c > index a0fa488bce84..8cca80094624 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -7460,7 +7460,7 @@ static void perf_sample_regs_user(struct perf_regs *regs_user, > if (user_mode(regs)) { > regs_user->abi = perf_reg_abi(current); > regs_user->regs = regs; > - } else if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER))) { > + } else if (is_user_task(current)) { > perf_get_regs_user(regs_user, regs); > } else { > regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE; > @@ -8100,7 +8100,7 @@ static u64 perf_virt_to_phys(u64 virt) > * Try IRQ-safe get_user_page_fast_only first. > * If failed, leave phys_addr as 0. > */ > - if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER))) { > + if (is_user_task(current)) { > struct page *p; > > pagefault_disable(); > @@ -8215,7 +8215,7 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs) > { > bool kernel = !event->attr.exclude_callchain_kernel; > bool user = !event->attr.exclude_callchain_user && > - !(current->flags & (PF_KTHREAD | PF_USER_WORKER)); > + is_user_task(current); > /* Disallow cross-task user callchains. */ > bool crosstask = event->ctx->task && event->ctx->task != current; > bool defer_user = IS_ENABLED(CONFIG_UNWIND_USER) && user &&