From: Petr Mladek <pmladek@suse.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Stephen Boyd <swboyd@chromium.org>,
Alexander Potapenko <glider@google.com>,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH next v1 1/2] dump_stack: move cpu lock to printk.c
Date: Thu, 3 Jun 2021 08:33:06 +0200 [thread overview]
Message-ID: <YLh3oqUiHGTtWJIC@alley> (raw)
In-Reply-To: <874keh3bsv.fsf@jogness.linutronix.de>
On Tue 2021-06-01 16:21:52, John Ogness wrote:
> On 2021-06-01, Petr Mladek <pmladek@suse.com> wrote:
> >> +void printk_cpu_lock(unsigned int *cpu_store, unsigned long *flags)
> >
> > I think about calling this printk_cpu_lock_irqsave() to make it clear
> > that it disables interrupts.
>
> Agreed.
>
> > Strictly speaking, it should be enough to disable preemption. If it is
> > safe when interrupted by NMI, it must be safe also when interrupted
> > by a normal interrupt.
> >
> > I guess that the interrupts are disabled because it reduces the risk
> > of nested (messed) backtraces.
>
> If it was just about synchronizing output triggered by sysreq, then it
> probably would be acceptable to leave interrupts active. But when atomic
> consoles are involved, we are talking about a crashing machine that is
> trying to get log messages out. Any interrupt is a risk that the machine
> may not survive long enough to return from that interruption.
Fair enough. It might be good to mention this motivation in the commit
message or in a code commentary. IMHO, it is always good to know
whether these things a must to have or if there is another reason.
Anyway, it was not obvious to me ;-)
Best Regards,
Petr
next prev parent reply other threads:[~2021-06-03 6:33 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-31 16:20 [PATCH next v1 0/2] introduce printk cpu lock John Ogness
2021-05-31 16:20 ` [PATCH next v1 1/2] dump_stack: move cpu lock to printk.c John Ogness
2021-05-31 16:30 ` John Ogness
2021-05-31 20:04 ` kernel test robot
2021-05-31 21:49 ` kernel test robot
2021-06-01 2:55 ` Sergey Senozhatsky
2021-06-01 6:58 ` John Ogness
2021-06-01 7:37 ` John Ogness
2021-06-01 13:29 ` Petr Mladek
2021-06-01 13:59 ` Petr Mladek
2021-06-01 14:21 ` John Ogness
2021-06-03 6:33 ` Petr Mladek [this message]
2021-05-31 16:20 ` [PATCH next v1 2/2] nmi_backtrace: use the printk cpu lock for show_regs() John Ogness
2021-06-01 14:25 ` Petr Mladek
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