From: Petr Mladek <pmladek@suse.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH printk v4 5/6] printk: convert @syslog_lock to mutex
Date: Wed, 21 Jul 2021 14:21:31 +0200 [thread overview]
Message-ID: <20210721122131.dlmkv7jsk2exj22y@pathway.suse.cz> (raw)
In-Reply-To: <20210715193359.25946-6-john.ogness@linutronix.de>
On Thu 2021-07-15 21:39:58, John Ogness wrote:
> @syslog_lock was a raw_spin_lock to simplify the transition of
> removing @logbuf_lock and the safe buffers. With that transition
> complete, and since all uses of @syslog_lock are within sleepable
> contexts, @syslog_lock can become a mutex.
>
> Note that until now register_console() would disable interrupts
> using irqsave, which implies that it may be called with interrupts
> disabled. And indeed, there is one possible call chain on parisc
> where this happens:
>
> handle_interruption(code=1) /* High-priority machine check (HPMC) */
> pdc_console_restart()
> pdc_console_init_force()
> register_console()
>
> However, register_console() calls console_lock(), which might sleep.
> So it has never been allowed to call register_console() from an
> atomic context and the above call chain is a bug.
>
> Note that the removal of read_syslog_seq_irq() is slightly changing
> the behavior of SYSLOG_ACTION_READ by testing against a possibly
> outdated @seq value. However, the value of @seq could have changed
> after the test, so it is not a new window. A follow-up commit closes
> this window.
>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Best Regards,
Petr
next prev parent reply other threads:[~2021-07-21 12:21 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 19:33 [PATCH printk v4 0/6] printk: remove safe buffers John Ogness
2021-07-15 19:33 ` [PATCH printk v4 1/6] lib/nmi_backtrace: explicitly serialize banner and regs John Ogness
2021-07-15 19:33 ` [PATCH printk v4 2/6] printk: track/limit recursion John Ogness
2021-07-15 19:33 ` [PATCH printk v4 3/6] printk: remove safe buffers John Ogness
2021-07-21 11:25 ` Petr Mladek
2021-09-02 16:48 ` Geert Uytterhoeven
2021-07-15 19:33 ` [PATCH printk v4 4/6] printk: remove NMI tracking John Ogness
2021-07-21 12:00 ` Petr Mladek
2021-07-21 12:46 ` John Ogness
2021-07-21 13:08 ` Petr Mladek
2021-07-21 13:23 ` John Ogness
2021-07-15 19:33 ` [PATCH printk v4 5/6] printk: convert @syslog_lock to mutex John Ogness
2021-07-21 12:21 ` Petr Mladek [this message]
2021-07-15 19:33 ` [PATCH printk v4 6/6] printk: syslog: close window between wait and read John Ogness
2021-07-21 12:43 ` Petr Mladek
2021-07-27 7:26 ` [PATCH printk v4 0/6] printk: remove safe buffers Petr Mladek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210721122131.dlmkv7jsk2exj22y@pathway.suse.cz \
--to=pmladek@suse.com \
--cc=john.ogness@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=senozhatsky@chromium.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).