linux-kernel - Re: [PATCH] ring-buffer: Handle resize in early boot up

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Message-ID: <Y5N/VM1u+Funtm0M@google.com>
Date:   Fri, 9 Dec 2022 11:32:52 -0700
From:   Ross Zwisler <zwisler@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] ring-buffer: Handle resize in early boot up

On Fri, Dec 09, 2022 at 01:13:57PM -0500, Steven Rostedt wrote:
> On Fri, 9 Dec 2022 09:57:48 -0700
> Ross Zwisler <zwisler@...gle.com> wrote:
> 
> > > +			if (cpu_id == smp_processor_id()) {
> > > +				rb_update_pages(cpu_buffer);
> > > +				migrate_enable();
> > > +			} else {
> > > +				migrate_enable();
> > > +				schedule_work_on(cpu_id,
> > > +						 &cpu_buffer->update_pages_work);
> > > +				wait_for_completion(&cpu_buffer->update_done);  
> > 
> > I ran with this patch on my test VM and hit the same Oops from the original
> > report.
> > 
> > I think the problem is that we're still trying to enable interrupts via
> > wait_for_completion():
> > 
> > wait_for_completion()
> >   wait_for_common()
> >     __wait_for_common()
> >       raw_spin_unlock_irq()
> >         _raw_spin_unlock_irq()
> >           __raw_spin_unlock_irq()
> >             local_irq_enable()
> > 
> > I'm testing on a QEMU VM with 4 virtual CPUs, if that helps WRT where work is
> > being scheduled (cpu_id == smp_processor_id).
> 
> Can you show the backtrace with that. Because when I triggered it, the
> other CPUs were not up and running. I'm testing this on a VM with 8 CPUs.

Ah, apologies, I think I got confused in my testing.  It is indeed working for
me now.

Thank you for the fix!

Tested-by: Ross Zwisler <zwisler@...gle.com>