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 v3 03/15] printk: add missing memory barrier to wake_up_klogd()
Date: Wed, 20 Apr 2022 14:34:50 +0200 [thread overview]
Message-ID: <Yl/9iDqRL3zKBoSJ@alley> (raw)
In-Reply-To: <20220419234637.357112-4-john.ogness@linutronix.de>
On Wed 2022-04-20 01:52:25, John Ogness wrote:
> It is important that any new records are visible to preparing
> waiters before the waker checks if the wait queue is empty.
> Otherwise it is possible that:
>
> - there are new records available
> - the waker sees an empty wait queue and does not wake
> - the preparing waiter sees no new records and begins to wait
>
> This is exactly the problem that the function description of
> waitqueue_active() warns about.
>
> Use wq_has_sleeper() instead of waitqueue_active() because it
> includes the necessary full memory barrier.
>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
Great catch! Looks good to me.
Reviewed-by: Petr Mladek <pmladek@suse.com>
Best Regards,
Petr
next prev parent reply other threads:[~2022-04-20 12:34 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-19 23:46 [PATCH printk v3 00/15] printk/for-next John Ogness
2022-04-19 23:46 ` [PATCH printk v3 01/15] printk: rename cpulock functions John Ogness
2022-04-19 23:46 ` [PATCH printk v3 02/15] printk: cpu sync always disable interrupts John Ogness
2022-04-19 23:46 ` [PATCH printk v3 03/15] printk: add missing memory barrier to wake_up_klogd() John Ogness
2022-04-20 12:34 ` Petr Mladek [this message]
2022-04-19 23:46 ` [PATCH printk v3 04/15] printk: wake up all waiters John Ogness
2022-04-20 12:36 ` Petr Mladek
2022-04-19 23:46 ` [PATCH printk v3 05/15] printk: wake waiters for safe and NMI contexts John Ogness
2022-04-20 13:55 ` Petr Mladek
2022-04-19 23:46 ` [PATCH printk v3 06/15] printk: get caller_id/timestamp after migration disable John Ogness
2022-04-19 23:46 ` [PATCH printk v3 07/15] printk: call boot_delay_msec() in printk_delay() John Ogness
2022-04-19 23:46 ` [PATCH printk v3 08/15] printk: add con_printk() macro for console details John Ogness
2022-04-20 14:01 ` Petr Mladek
2022-04-19 23:46 ` [PATCH printk v3 09/15] printk: refactor and rework printing logic John Ogness
2022-04-20 14:55 ` Petr Mladek
2022-04-19 23:46 ` [PATCH printk v3 10/15] printk: move buffer definitions into console_emit_next_record() caller John Ogness
2022-04-19 23:46 ` [PATCH printk v3 11/15] printk: add pr_flush() John Ogness
2022-04-20 15:10 ` Petr Mladek
2022-04-19 23:46 ` [PATCH printk v3 12/15] printk: add functions to prefer direct printing John Ogness
2022-04-19 23:46 ` [PATCH printk v3 13/15] printk: add kthread console printers John Ogness
2022-04-20 17:53 ` Petr Mladek
2022-04-20 20:02 ` John Ogness
2022-04-21 14:25 ` Petr Mladek
2022-04-19 23:46 ` [PATCH printk v3 14/15] printk: extend console_lock for proper kthread support John Ogness
2022-04-20 2:13 ` kernel test robot
2022-04-20 13:32 ` John Ogness
2022-04-20 13:32 ` John Ogness
2022-04-20 4:04 ` kernel test robot
2022-04-21 12:41 ` Petr Mladek
2022-04-21 14:30 ` John Ogness
2022-04-22 13:03 ` Petr Mladek
2022-04-22 14:14 ` John Ogness
2022-04-22 15:15 ` Petr Mladek
2022-04-22 21:25 ` John Ogness
2022-04-25 15:18 ` Petr Mladek
2022-04-25 19:10 ` John Ogness
2022-04-19 23:46 ` [PATCH printk v3 15/15] printk: remove @console_locked John Ogness
2022-04-21 12:46 ` Petr Mladek
2022-04-21 14:40 ` [PATCH printk v3 00/15] printk/for-next Petr Mladek
2022-04-21 15:02 ` John Ogness
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