From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: John Ogness <john.ogness@linutronix.de>
Cc: Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Luis Chamberlain <mcgrof@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
"Guilherme G. Piccoli" <gpiccoli@igalia.com>
Subject: Re: [PATCH printk v2 09/11] panic: Add atomic write enforcement to oops
Date: Wed, 20 Sep 2023 16:28:38 +0300 [thread overview]
Message-ID: <ZQrzhh62pDB5yUyi@smile.fi.intel.com> (raw)
In-Reply-To: <20230919230856.661435-10-john.ogness@linutronix.de>
On Wed, Sep 20, 2023 at 01:14:54AM +0206, John Ogness wrote:
> Invoke the atomic write enforcement functions for oops to
> ensure that the information gets out to the consoles.
>
> Since there is no single general function that calls both
> oops_enter() and oops_exit(), the nesting feature of atomic
> write sections is taken advantage of in order to guarantee
> full coverage between the first oops_enter() and the last
> oops_exit().
>
> It is important to note that if there are any legacy consoles
> registered, they will be attempting to directly print from the
> printk-caller context, which may jeopardize the reliability of
> the atomic consoles. Optimally there should be no legacy
> consoles registered.
...
> + if (atomic_read(&oops_cpu) == smp_processor_id()) {
> + oops_nesting--;
> + if (oops_nesting == 0) {
> + atomic_set(&oops_cpu, -1);
Between read and set the variable can change, can't it?
If not, why this variable is atomic then? Or, why it's not a problem?
If the latter is the case, perhaps a comment to explain this?
> + /* Exit outmost atomic section. */
> + nbcon_atomic_exit(NBCON_PRIO_EMERGENCY, oops_prev_prio);
> + }
> + }
> + put_cpu();
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2023-09-20 13:28 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-19 23:08 [PATCH printk v2 00/11] wire up nbcon atomic printing John Ogness
2023-09-19 23:08 ` [PATCH printk v2 01/11] printk: Make console_is_usable() available to nbcon John Ogness
2023-09-22 8:33 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 02/11] printk: Let console_is_usable() handle nbcon John Ogness
2023-09-22 8:37 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 03/11] printk: Add @flags argument for console_is_usable() John Ogness
2023-09-22 8:41 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 04/11] printk: nbcon: Provide functions to mark atomic write sections John Ogness
2023-09-22 9:33 ` Petr Mladek
2023-09-25 9:25 ` John Ogness
2023-09-25 16:04 ` Petr Mladek
2023-10-05 12:51 ` John Ogness
2023-10-06 12:51 ` panic context: was: " Petr Mladek
2023-10-06 12:53 ` Petr Mladek
2023-10-08 10:13 ` John Ogness
2023-10-09 15:32 ` Petr Mladek
2023-10-10 16:02 ` John Ogness
2023-10-16 8:58 ` Dave Young
2023-10-16 10:09 ` John Ogness
2023-10-06 15:52 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 05/11] printk: nbcon: Provide function for atomic flushing John Ogness
2023-09-22 12:32 ` Petr Mladek
2023-09-25 11:11 ` John Ogness
2023-09-19 23:08 ` [PATCH printk v2 06/11] printk: nbcon: Wire up nbcon console " John Ogness
2023-09-22 17:41 ` Petr Mladek
2023-09-25 13:37 ` John Ogness
2023-09-26 12:14 ` Petr Mladek
2023-10-05 13:59 ` John Ogness
2023-09-19 23:08 ` [PATCH printk v2 07/11] printk: nbcon: Wire up nbcon into console_flush_all() John Ogness
2023-09-26 11:34 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 08/11] panic: Add atomic write enforcement to warn/panic John Ogness
2023-09-27 12:02 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 09/11] panic: Add atomic write enforcement to oops John Ogness
2023-09-19 23:36 ` John Ogness
2023-09-20 13:28 ` Andy Shevchenko [this message]
2023-09-20 14:20 ` John Ogness
2023-09-20 14:45 ` Andy Shevchenko
2023-09-27 13:15 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 10/11] rcu: Add atomic write enforcement for rcu stalls John Ogness
2023-09-27 15:00 ` Petr Mladek
2023-09-19 23:08 ` [PATCH printk v2 11/11] lockdep: Add atomic write enforcement for lockdep splats John Ogness
2023-09-29 8:31 ` Petr Mladek
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