From mboxrd@z Thu Jan  1 00:00:00 1970
From: Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 00/50] Add log level to show_stack()
Date: Wed, 13 Nov 2019 10:32:14 -0500
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To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Juri Lelli <juri.lelli@redhat.com>, linux-sh@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>, Ben Segall <bsegall@google.com>, Guo Ren <guoren@kernel.org>, Pavel Machek <pavel@ucw.cz>, Vincent Guittot <vincent.guittot@linaro.org>, Paul Burton <paulburton@kernel.org>, Dmitry Safonov <dima@arista.com>, Michael Ellerman <mpe@ellerman.id.au>, Geert Uytterhoeven <geert@linux-m68k.org>, Mel Gorman <mgorman@suse.de>, Jiri Slaby <jslaby@suse.com>, Matt Turner <mattst88@gmail.com>, uclinux-h8-devel@lists.sourceforge.jp, Len Brown <len.brown@intel.com>, linux-pm@vger.kernel.org, Heiko Carstens <heiko.carstens@de.ibm.com>, linux-um@lists.infradead.org, Thomas Gleixner <tglx@linutronix.de>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Richard Henderson <rth@twiddle.net>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, linux-kerne

On Tue, 12 Nov 2019 13:44:47 +0900
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:

> > > I do recall that we talked about per-CPU printk state bit which would
> > > start/end "just print it" section. We probably can extend it to "just
> > > log_store" type of functionality. Doesn't look like a very bad idea.  
> > 
> > The problem with per-CPU printk is that we would need to disable
> > interrupts.  
> 
> Or disable preemption and have loglevel per-CPU and per-context.
> preempt_count can navigate us to the right context loglevel on
> particular CPU. I'm talking here only about backtrace (error)
> reporting contexts. Those can be atomic perfectly fine.

With my real-time hat on, I'm totally against disabling of preemption
for this purpose.

-- Steve