From: Peter Zijlstra <peterz@infradead.org>
To: Radoslaw Zielonek <radoslaw.zielonek@gmail.com>
Cc: rostedt@goodmis.org, mhiramat@kernel.org,
mathieu.desnoyers@efficios.com, mingo@redhat.com,
juri.lelli@redhat.com, vincent.guittot@linaro.org,
dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de,
vschneid@redhat.com, song@kernel.org, jolsa@kernel.org,
ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@linux.dev, eddyz87@gmail.com, yonghong.song@linux.dev,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me,
haoluo@google.com, mattbobrowski@google.com, qyousef@layalina.io,
tiozhang@didiglobal.com, elver@google.com,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [RFC] Printk deadlock in bpf trace called from scheduler context
Date: Mon, 29 Jul 2024 14:27:26 +0200 [thread overview]
Message-ID: <20240729122726.GA33588@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20240729114608.1792954-2-radoslaw.zielonek@gmail.com>
On Mon, Jul 29, 2024 at 01:46:09PM +0200, Radoslaw Zielonek wrote:
> I am currently working on a syzbot-reported bug where bpf
> is called from trace_sched_switch. In this scenario, we are still within
> the scheduler context, and calling printk can create a deadlock.
>
> I am uncertain about the best approach to fix this issue.
It's been like this forever, it doesn't need fixing, because tracepoints
shouldn't be doing printk() in the first place.
> Should we simply forbid such calls, or perhaps we should replace printk
> with printk_deferred in the bpf where we are still in scheduler context?
Not doing printk() is best.
next prev parent reply other threads:[~2024-07-29 12:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-29 11:46 Radoslaw Zielonek
2024-07-29 12:27 ` Peter Zijlstra [this message]
2024-07-29 12:45 ` Marco Elver
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