From: John Ogness <john.ogness@linutronix.de>
To: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Petr Mladek <pmladek@suse.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 09:37:08 +0200 [thread overview]
Message-ID: <87v96y2fyz.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <87y2bu2hqp.fsf@jogness.linutronix.de>
On 2021-06-01, John Ogness <john.ogness@linutronix.de> wrote:
>> Is there any particular reason this does
>>
>> preempt_disable();
>> cpu = smp_processor_id();
>> local_irq_safe();
>>
>> instead of
>>
>> local_irq_safe();
>> cpu = raw_smp_processor_id();
>>
>> ?
>
> If the lock is owned by another CPU, there is no need to disable
> interrupts for this CPU. (The local_irq_save() is conditional.)
The cpu lock implementation from dump_stack() also keeps preemption
continually enabled while spinning. I used the cpu lock implementation
from PREEMPT_RT. But for my v2 I will adopt the same ordering from
dump_stack(), as you are suggesting.
Thanks for pointing that out.
John Ogness
next prev parent reply other threads:[~2021-06-01 7:37 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 [this message]
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
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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