From: Jens Axboe <axboe@kernel.dk>
To: Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
bpf@vger.kernel.org, x86@kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrii Nakryiko <andrii@kernel.org>,
Indu Bhagat <indu.bhagat@oracle.com>,
"Jose E. Marchesi" <jemarch@gnu.org>,
Beau Belgrave <beaub@linux.microsoft.com>,
Jens Remus <jremus@linux.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v11 03/11] perf: Use current->flags & PF_KTHREAD instead of current->mm == NULL
Date: Thu, 26 Jun 2025 07:48:40 -0600 [thread overview]
Message-ID: <a3b456f2-deeb-45c9-b509-23bbe5e96cfd@kernel.dk> (raw)
In-Reply-To: <20250625231622.172100822@goodmis.org>
On 6/25/25 5:15 PM, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> 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
next prev parent reply other threads:[~2025-06-26 13:48 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-25 23:15 [PATCH v11 00/11] perf: Support the deferred unwinding infrastructure Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 01/11] perf: Remove get_perf_callchain() init_nr argument Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 02/11] perf: Have get_perf_callchain() return NULL if crosstask and user are set Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 03/11] perf: Use current->flags & PF_KTHREAD instead of current->mm == NULL Steven Rostedt
2025-06-26 13:48 ` Jens Axboe [this message]
2025-06-26 14:11 ` Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 04/11] perf: Simplify get_perf_callchain() user logic Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 05/11] perf: Skip user unwind if the task is a kernel thread Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 06/11] perf: Support deferred user callchains Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 07/11] perf: Support deferred user callchains for per CPU events Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 08/11] perf tools: Minimal CALLCHAIN_DEFERRED support Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 09/11] perf record: Enable defer_callchain for user callchains Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 10/11] perf script: Display PERF_RECORD_CALLCHAIN_DEFERRED Steven Rostedt
2025-06-25 23:15 ` [PATCH v11 11/11] perf tools: Merge deferred user callchains Steven Rostedt
2025-06-26 14:49 ` [PATCH v11 00/11] perf: Support the deferred unwinding infrastructure Steven Rostedt
2025-06-26 14:50 ` [PATCH v11 10/11] perf script: Display PERF_RECORD_CALLCHAIN_DEFERRED Steven Rostedt
2025-06-26 14:51 ` [PATCH v11 11/11] perf tools: Merge deferred user callchains Steven Rostedt
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