linux-kernel - Re: [PATCH] tracing: Mitigate possible softlockup in __tracing

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Message-ID: <20240827075241.5cd652ae@rorschach.local.home>
Date: Tue, 27 Aug 2024 07:52:41 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Zheng Yejian <zhengyejian@...weicloud.com>
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Mitigate possible softlockup in
 __tracing_open()

On Tue, 27 Aug 2024 09:29:55 +0800
Zheng Yejian <zhengyejian@...weicloud.com> wrote:

 
> > This is the wrong place to put this. If the problem is with
> > tracing_iter_reset(), then add it there.
> > 
> > 	while (ring_buffer_iter_peek(buf_iter, &ts)) {
> > 		if (ts >= iter->array_buffer->time_start)
> > 			break;
> > 		entries++;
> > 		ring_buffer_iter_advance(buf_iter);
> > 		/* This could be a big loop */
> > 		cond_resched();  
> 
> Do resched check every event peek, I'm afraid there will
> be too many 're-schedule'.

cond_resched() as the name suggests only schedules conditionally if
NEED_RESCHED is set. This isn't a fast path (obviously, as it requires
a cond_resched).

-- Steve