linux-kernel - Re: [PATCH] tracing: Fix tracing_marker may trigger page fault during preempt

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Message-ID: <20250902101454.08ac4b51@batman.local.home>
Date: Tue, 2 Sep 2025 10:14:54 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Luo Gengkun <luogengkun@...weicloud.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
 mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] tracing: Fix tracing_marker may trigger page fault
 during preempt_disable

On Tue, 2 Sep 2025 11:47:32 +0800
Luo Gengkun <luogengkun@...weicloud.com> wrote:

> > If this does not check the preempt flag, it is a problem.
> > Maybe arm64 needs to do fixup and abort instead of do_mem_abort()?  
> 
> My kernel was built without CONFIG_PREEMPT_COUNT, so the preempt_disable()
> does nothing more than act as a barrier. In this case, it can pass the
> check by schedule(). Perhaps this is another issue?

This is why I never triggered it. I always have PREEMPT_COUNT enabled.
I have tests that test without it, but I don't think those tests access
trace_marker, and if they do, they don't stress it.

-- Steve