netdev - Re: [BUG] possible deadlock in __schedule (with reproducer available)

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Message-ID: <20241124224441.5614c15a@rorschach.local.home>
Date: Sun, 24 Nov 2024 22:44:41 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ruan Bonan
 <bonan.ruan@...us.edu>, "mingo@...hat.com" <mingo@...hat.com>,
 "will@...nel.org" <will@...nel.org>, "longman@...hat.com"
 <longman@...hat.com>, "boqun.feng@...il.com" <boqun.feng@...il.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "kpsingh@...nel.org" <kpsingh@...nel.org>, "mattbobrowski@...gle.com"
 <mattbobrowski@...gle.com>, "ast@...nel.org" <ast@...nel.org>,
 "daniel@...earbox.net" <daniel@...earbox.net>, "andrii@...nel.org"
 <andrii@...nel.org>, "martin.lau@...ux.dev" <martin.lau@...ux.dev>,
 "eddyz87@...il.com" <eddyz87@...il.com>, "song@...nel.org"
 <song@...nel.org>, "yonghong.song@...ux.dev" <yonghong.song@...ux.dev>,
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 "jolsa@...nel.org" <jolsa@...nel.org>, "mhiramat@...nel.org"
 <mhiramat@...nel.org>, "mathieu.desnoyers@...icios.com"
 <mathieu.desnoyers@...icios.com>, "bpf@...r.kernel.org"
 <bpf@...r.kernel.org>, "linux-trace-kernel@...r.kernel.org"
 <linux-trace-kernel@...r.kernel.org>, "netdev@...r.kernel.org"
 <netdev@...r.kernel.org>, Fu Yeqi <e1374359@...us.edu>
Subject: Re: [BUG] possible deadlock in __schedule (with reproducer
 available)

On Sun, 24 Nov 2024 22:30:45 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> > > Ack. BPF should not be causing deadlocks by doing code called from
> > > tracepoints.    
> > 
> > I sense so much BPF love here that it diminishes the ability to read
> > stack traces :)  
> 
> You know I love BPF ;-)  I do recommend it when I feel it's the right
> tool for the job.

BTW, I want to apologize if my email sounded like an attack on BPF.
That wasn't my intention. It was more about Peter's response being
so short, where the submitter may not understand his response. It's not
up to Peter to explain himself. As I said, this isn't his problem.

I figured I would fill in the gap. As I fear with more people using BPF,
when some bug happens when they attach a BPF program somewhere, they
then blame the code that they attached to. If this was titled "Possible
deadlock when attaching BPF program to scheduler" and was sent to the
BPF folks, I would not have any issue with it. But it was sent to the
scheduler maintainers.

We need to teach people that if a bug happens because they attach a BPF
program somewhere, they first notify the BPF folks. Then if it really
ends up being a bug where the BPF program was attached, it should be
the BPF folks that inform that subsystem maintainers. Not the original
submitter.

Cheers,

-- Steve