Re: [PATCH v2 3/3] printk/nmi: Prevent deadlock when accessing the main log buffer in NMI
From: Sergey Senozhatsky
Date: Thu Jun 28 2018 - 21:47:18 EST
On (06/28/18 11:41), Petr Mladek wrote:
> >
> > A side note: This nesting also handles recursive printk-s for us.
> >
> > NMI:
> > printk_nmi_enter
> > ftrace_dump
> > printk_nmi_direct_enter
> > vprintk_func
> > spin_lock(logbuf_lock)
> > vprintk_store
> > vsprintf
> > WARN_ON
> > vprintk_func
> > vprintk_nmi
>
> Uff, it seems that the current design is "good" at lest from some
> points of view.
yep yep
> > > + len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
> > > + raw_spin_unlock(&logbuf_lock);
> > > + defer_console();
> > > + return len;
> > > + }
> >
> > So, maybe, something a bit better than defer_console().
>
> I am not super happy with the name either. But wakeup_console(),
> schedule_console(), or queue_console() looked confusing.
Hmm. defer_console() makes me think that we are dealing with that
fbcon=nodefer and deferred console takeover thing here.
So I summon Mr. Rostedt!
Does schedule_console_output() look bad?
What about defer_console_output()?
Any other ideas?
-ss