From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
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: Tue, 01 Jun 2021 16:21:52 +0200 [thread overview]
Message-ID: <874keh3bsv.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <YLY9NR7C1IFuNI4A@alley>
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.
John Ogness
next prev parent reply other threads:[~2021-06-01 14:21 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 [this message]
2021-06-03 6:33 ` Petr Mladek
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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