From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Andrew Morton <akpm@linux-foundation.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
x86@kernel.org, Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Indu Bhagat <indu.bhagat@oracle.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
linux-perf-users@vger.kernel.org, Mark Brown <broonie@kernel.org>,
linux-toolchains@vger.kernel.org, Jordan Rome <jordalgo@meta.com>,
Sam James <sam@gentoo.org>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Jens Remus <jremus@linux.ibm.com>,
Florian Weimer <fweimer@redhat.com>,
Andy Lutomirski <luto@kernel.org>, Weinan Liu <wnliu@google.com>,
Blake Jones <blakejones@google.com>,
Beau Belgrave <beaub@linux.microsoft.com>,
"Jose E. Marchesi" <jemarch@gnu.org>
Subject: Re: [PATCH v5 11/17] perf: Simplify get_perf_callchain() user logic
Date: Thu, 24 Apr 2025 13:28:00 -0400 [thread overview]
Message-ID: <20250424132800.49160c2e@gandalf.local.home> (raw)
In-Reply-To: <20250424163607.GE18306@noisy.programming.kicks-ass.net>
On Thu, 24 Apr 2025 18:36:07 +0200
Peter Zijlstra <peterz@infradead.org> wrote:
> > +++ b/kernel/events/callchain.c
> > @@ -246,22 +246,20 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
> >
> > if (user) {
> > if (!user_mode(regs)) {
> > - if (current->mm)
> > - regs = task_pt_regs(current);
> > - else
> > - regs = NULL;
> > + if (!current->mm)
> > + goto exit_put;
> > + regs = task_pt_regs(current);
>
> I'm thinking this might be one of those is-kthread test written as
> has-mm, and they're broken.
>
> Notably things like the io-uring kthreads do have mm.
Would there ever be a case where:
current->mm == NULL && !(current->flags & PF_KTHREAD)
?
That is, do we still need to check for current->mm if it's not a kernel
thread, or can we assume it exists?
-- Steve
next prev parent reply other threads:[~2025-04-24 17:26 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-24 16:25 [PATCH v5 00/17] perf: Deferred unwinding of user space stack traces Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 01/17] unwind_user: Add user space unwinding API Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 02/17] unwind_user: Add frame pointer support Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 03/17] unwind_user/x86: Enable frame pointer unwinding on x86 Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 04/17] perf/x86: Rename and move get_segment_base() and make it global Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 05/17] unwind_user: Add compat mode frame pointer support Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 06/17] unwind_user/x86: Enable compat mode frame pointer unwinding on x86 Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 07/17] unwind_user/deferred: Add unwind_deferred_trace() Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 08/17] unwind_user/deferred: Add unwind cache Steven Rostedt
2025-04-24 19:00 ` Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 09/17] perf: Remove get_perf_callchain() init_nr argument Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 10/17] perf: Have get_perf_callchain() return NULL if crosstask and user are set Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 11/17] perf: Simplify get_perf_callchain() user logic Steven Rostedt
2025-04-24 16:36 ` Peter Zijlstra
2025-04-24 17:28 ` Steven Rostedt [this message]
2025-04-24 17:42 ` Mathieu Desnoyers
2025-04-24 17:47 ` Steven Rostedt
2025-04-25 7:13 ` Peter Zijlstra
2025-04-24 16:25 ` [PATCH v5 12/17] perf: Skip user unwind if !current->mm Steven Rostedt
2025-04-24 16:37 ` Peter Zijlstra
2025-04-24 17:01 ` Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 13/17] perf: Support deferred user callchains Steven Rostedt
2025-04-24 16:38 ` Peter Zijlstra
2025-04-24 17:16 ` Steven Rostedt
2025-04-25 15:24 ` Namhyung Kim
2025-04-25 16:58 ` Steven Rostedt
2025-04-28 20:42 ` Namhyung Kim
2025-04-28 22:02 ` Steven Rostedt
2025-04-29 0:29 ` Namhyung Kim
2025-04-29 14:00 ` Steven Rostedt
2025-05-08 16:03 ` Steven Rostedt
2025-05-08 18:44 ` Namhyung Kim
2025-05-08 18:49 ` Mathieu Desnoyers
2025-05-08 18:54 ` Steven Rostedt
2025-05-09 12:23 ` Mathieu Desnoyers
2025-05-09 15:45 ` Namhyung Kim
2025-05-09 15:55 ` Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 14/17] perf tools: Minimal CALLCHAIN_DEFERRED support Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 15/17] perf record: Enable defer_callchain for user callchains Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 16/17] perf script: Display PERF_RECORD_CALLCHAIN_DEFERRED Steven Rostedt
2025-04-24 16:25 ` [PATCH v5 17/17] perf tools: Merge deferred user callchains Steven Rostedt
2025-04-24 17:04 ` [PATCH v5 00/17] perf: Deferred unwinding of user space stack traces Steven Rostedt
2025-04-24 18:32 ` Miguel Ojeda
2025-04-24 18:41 ` Steven Rostedt
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