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From: Steven Rostedt <rostedt@goodmis.org>
To: Runping Lai <runpinglai@google.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Wattson CI <wattson-external@google.com>,
	kernel-team@android.com, linux-kernel@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org,
	Luo Gengkun <luogengkun@huaweicloud.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v1] Revert "tracing: Fix tracing_marker may trigger page fault during preempt_disable"
Date: Tue, 7 Oct 2025 15:43:08 -0400	[thread overview]
Message-ID: <20251007154308.5b158d04@gandalf.local.home> (raw)
In-Reply-To: <CABgk4RQwGsn4CdP0K+_7A0j7RVOiHNfoF1ESk17wEuzCea16pA@mail.gmail.com>

On Tue, 7 Oct 2025 11:19:34 -0700
Runping Lai <runpinglai@google.com> wrote:


> Hey Steve,
> 
> On Pixel6, CONFIG_PREEMPT is set. And CONFIG_PREEMPT_NONE
> is not set. I'll paste the full PREEMPT configs:

Hmm, now I'm curious to why _nofault() does't work but inatomic does.

> 
> >
> > The original code is buggy, but if this is causing a regression, then we
> > likely need to do something else, like copy in a pre-allocated buffer?  
> 
> Sounds like a good plan. Before the long term fix, can we please
> revert this commit?

Not that easy as the old way has a legitimate bug in it.

Could you see if adding pagefault_disable() and pagefault_enable() around
the __copy_from_user_inatomic() works for you? Or does that have the same
problem?

I do have a working solution, but it isn't trivial.

-- Steve


  reply	other threads:[~2025-10-07 19:48 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-10-07  0:34 Runping Lai
2025-10-07  2:10 ` Steven Rostedt
2025-10-07 18:19   ` Runping Lai
2025-10-07 19:43     ` Steven Rostedt [this message]
2025-10-07 20:31       ` Steven Rostedt
2025-10-07 21:42         ` Steven Rostedt
2025-10-07 23:25           ` Runping Lai
2025-10-08  0:21             ` Steven Rostedt
2025-10-08 16:32             ` Steven Rostedt
2025-10-08 17:12               ` Runping Lai

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