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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a3b456f2-deeb-45c9-b509-23bbe5e96cfd@kernel.dk \
--to=axboe@kernel.dk \
--cc=akpm@linux-foundation.org \
--cc=andrii@kernel.org \
--cc=beaub@linux.microsoft.com \
--cc=bpf@vger.kernel.org \
--cc=indu.bhagat@oracle.com \
--cc=jemarch@gnu.org \
--cc=jolsa@kernel.org \
--cc=jpoimboe@kernel.org \
--cc=jremus@linux.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-trace-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mhiramat@kernel.org \
--cc=mingo@kernel.org \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.