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
Subject: Re: [PATCH printk-rework 08/14] printk: add syslog_lock
Date: Tue, 23 Feb 2021 15:38:42 +0100 [thread overview]
Message-ID: <YDUTcplrbHJ83afV@alley> (raw)
In-Reply-To: <87czwst5mb.fsf@jogness.linutronix.de>
On Mon 2021-02-22 17:43:56, John Ogness wrote:
> On 2021-02-22, Petr Mladek <pmladek@suse.com> wrote:
> >>>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> >>>> index 20c21a25143d..401df370832b 100644
> >>>> --- a/kernel/printk/printk.c
> >>>> +++ b/kernel/printk/printk.c
> >>>> +/* Return a consistent copy of @syslog_seq. */
> >>>> +static u64 read_syslog_seq_irq(void)
> >>>> +{
> >>>> + u64 seq;
> >>>> +
> >>>> + raw_spin_lock_irq(&syslog_lock);
> >>>> + seq = syslog_seq;
> >>>> + raw_spin_unlock_irq(&syslog_lock);
> >>>
> >>> Is there any particular reason to disable interrupts here?
> >>>
> >>> It would make sense only when the lock could be taken in IRQ
> >>> context. Then we would need to always disable interrupts when
> >>> the lock is taken. And if it is taken in IRQ context, we would
> >>> need to safe flags.
> >
> > Note that console_lock was a spinlock in 2.3.15.pre1. I see it defined
> > in kernel/printk.c as:
> >
> > spinlock_t console_lock = SPIN_LOCK_UNLOCKED;
> >
> > But it is a sleeping semaphore these days. As a result,
> > register_console(), as it is now, must not be called in an interrupt
> > context.
>
> OK. So I will change read_syslog_seq_irq() to not disable interrupts. As
> you suggested, we can fix the rest when we remove the safe buffers.
I do not have strong opinion any longer. The disabled interrupts
should not change anything, except theoretically for the parisc
emergency console.
Maybe keep the disabled interrupts there until we have a better solution
for parisc.
Best Regards,
Petr
next prev parent reply other threads:[~2021-02-23 14:39 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-18 8:18 [PATCH printk-rework 00/14] printk: remove logbuf_lock John Ogness
2021-02-18 8:18 ` [PATCH printk-rework 01/14] printk: limit second loop of syslog_print_all John Ogness
2021-02-18 16:15 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 02/14] printk: kmsg_dump: remove unused fields John Ogness
2021-02-18 16:18 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 03/14] printk: refactor kmsg_dump_get_buffer() John Ogness
2021-02-18 8:18 ` [PATCH printk-rework 04/14] printk: consolidate kmsg_dump_get_buffer/syslog_print_all code John Ogness
2021-02-19 12:28 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 05/14] printk: introduce CONSOLE_LOG_MAX for improved multi-line support John Ogness
2021-02-19 12:44 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 06/14] printk: use seqcount_latch for clear_seq John Ogness
2021-02-18 8:18 ` [PATCH printk-rework 07/14] printk: use atomic64_t for devkmsg_user.seq John Ogness
2021-02-19 12:59 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 08/14] printk: add syslog_lock John Ogness
2021-02-19 13:30 ` Petr Mladek
2021-02-19 14:45 ` John Ogness
2021-02-19 16:33 ` John Ogness
2021-02-21 21:39 ` Helge Deller
2021-02-22 16:28 ` Petr Mladek
2021-02-23 12:22 ` Helge Deller
2021-02-23 14:23 ` Petr Mladek
2021-02-23 14:45 ` Helge Deller
2021-02-22 16:05 ` Petr Mladek
2021-02-22 16:43 ` John Ogness
2021-02-23 14:38 ` Petr Mladek [this message]
2021-02-18 8:18 ` [PATCH printk-rework 09/14] printk: introduce a kmsg_dump iterator John Ogness
2021-02-19 15:56 ` Petr Mladek
2021-02-19 16:50 ` Michael Kelley
2021-02-19 17:57 ` synchronization model: was: " Petr Mladek
2021-02-24 12:27 ` John Ogness
2021-02-24 15:40 ` John Ogness
2021-02-25 12:33 ` Petr Mladek
2021-02-26 8:36 ` John Ogness
2021-02-26 9:48 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 10/14] um: synchronize kmsg_dumper John Ogness
2021-02-18 8:18 ` [PATCH printk-rework 11/14] printk: remove logbuf_lock John Ogness
2021-02-23 11:44 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 12/14] printk: kmsg_dump: remove _nolock() variants John Ogness
2021-02-23 11:51 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 13/14] printk: kmsg_dump: use kmsg_dump_rewind John Ogness
2021-02-23 11:53 ` Petr Mladek
2021-02-18 8:18 ` [PATCH printk-rework 14/14] printk: console: remove unnecessary safe buffer usage John Ogness
2021-02-23 12:55 ` Petr Mladek
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