linux-kernel - Re: [PATCH v3] ring-buffer: Prevent inconsistent operation on cpu_buffer->resize

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Message-ID: <20230411223206.0bc5794e@gandalf.local.home>
Date:   Tue, 11 Apr 2023 22:32:06 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Tze-nan Wu (吳澤南)" <Tze-nan.Wu@...iatek.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-trace-kernel@...r.kernel.org" 
        <linux-trace-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "Cheng-Jui Wang (王正睿)" 
        <Cheng-Jui.Wang@...iatek.com>,
        "paulmck@...nel.org" <paulmck@...nel.org>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        "Bobule Chang (張弘義)" <bobule.chang@...iatek.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "mhiramat@...nel.org" <mhiramat@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        "npiggin@...il.com" <npiggin@...il.com>
Subject: Re: [PATCH v3] ring-buffer: Prevent inconsistent operation on
 cpu_buffer->resize_disabled

On Wed, 12 Apr 2023 02:27:53 +0000
Tze-nan Wu (吳澤南) <Tze-nan.Wu@...iatek.com> wrote:

> > > @@ -5368,7 +5372,7 @@ void ring_buffer_reset_online_cpus(struct
> > > trace_buffer *buffer)
> > >       /* Make sure all commits have finished */
> > >       synchronize_rcu();
> > > 
> > > -     for_each_online_buffer_cpu(buffer, cpu) {
> > > +     for_each_cpu_and(cpu, buffer->cpumask, &reset_online_cpumask)  
> 
> Maybe we should use for_each_buffer_cpu(buffer, cpu) here?
> since a CPU may also came offline during synchronize_rcu().

Yeah, I guess that works too (not looking at the code at the moment though).

-- Steve

> 
> > > {
> > >               cpu_buffer = buffer->buffers[cpu];  
> >