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Thu, 26 Jun 2025 06:48:43 -0700 (PDT) Message-ID: Date: Thu, 26 Jun 2025 07:48:40 -0600 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 03/11] perf: Use current->flags & PF_KTHREAD instead of current->mm == NULL To: Steven Rostedt , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, x86@kernel.org Cc: Masami Hiramatsu , Mathieu Desnoyers , Josh Poimboeuf , Peter Zijlstra , Ingo Molnar , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Andrii Nakryiko , Indu Bhagat , "Jose E. Marchesi" , Beau Belgrave , Jens Remus , Linus Torvalds , Andrew Morton References: <20250625231541.584226205@goodmis.org> <20250625231622.172100822@goodmis.org> Content-Language: en-US From: Jens Axboe In-Reply-To: <20250625231622.172100822@goodmis.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/25/25 5:15 PM, Steven Rostedt wrote: > From: Steven Rostedt > > To determine if a task is a kernel thread or not, it is more reliable to > use (current->flags & PF_KTHREAD) than to rely on current->mm being NULL. > That is because some kernel tasks (io_uring helpers) may have a mm field. This commit message is very odd, imho, and wrong. To check if it's a kernel thread yes you should use PF_KTHREAD, but that has nothing to do with PF_USER_WORKER. In fact, as mentioned in a previous reply, current->mm may be non-NULL for a kthread as well, if it's done kthread_use_mm(). If the current check for "is kernel thread" was using ->mm to gauge then, then the current check was just wrong, period. -- Jens Axboe