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

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Message-ID: <20221209131357.5e4f6d01@gandalf.local.home>
Date:   Fri, 9 Dec 2022 13:13:57 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ross Zwisler <zwisler@...gle.com>
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, 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.

-- Steve