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 v2 31/38] printk: register_console: use srcu console list iterator
Date: Wed, 26 Oct 2022 10:20:37 +0200 [thread overview]
Message-ID: <Y1jt1Xd23FIj1kbF@alley> (raw)
In-Reply-To: <20221019145600.1282823-32-john.ogness@linutronix.de>
On Wed 2022-10-19 17:01:53, John Ogness wrote:
> Use srcu console list iteration for console list traversal. Now
> the traversal at the beginning of register_console() is safe.
>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
That said, I think that we could omit this patch. It does not harm.
It prevents a crash when iterating the list but it is only small part
of the races here.
For example, it sets "realcon_enabled" but the list might change before the
value is used. Also the later hlist_empty(&console_list) and
!console_first->device checks are not secure against each other.
The real solution is the introduction of console_list_lock in 33th
patch. That patch removes the rcu read lock. From this POV, this patch
is just unnecessary churn.
Best Regards,
Petr
next prev parent reply other threads:[~2022-10-26 8:20 UTC|newest]
Thread overview: 151+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-19 14:55 [PATCH printk v2 00/38] reduce console_lock scope John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-19 14:55 ` [PATCH printk v2 01/38] serial: kgdboc: Lock console list in probe function John Ogness
2022-10-19 15:41 ` Greg Kroah-Hartman
2022-10-24 5:22 ` Sergey Senozhatsky
2022-10-25 0:34 ` Doug Anderson
2022-10-19 14:55 ` [PATCH printk v2 02/38] printk: Convert console_drivers list to hlist John Ogness
2022-10-19 15:44 ` Greg Kroah-Hartman
2022-10-19 21:46 ` John Ogness
2022-10-20 7:43 ` Greg Kroah-Hartman
2022-10-20 12:36 ` Petr Mladek
2022-10-24 5:23 ` Sergey Senozhatsky
2022-10-19 14:55 ` [PATCH printk v2 03/38] printk: Prepare for SRCU console list protection John Ogness
2022-10-19 15:16 ` Miguel Ojeda
2022-10-19 17:12 ` Paul E. McKenney
2022-10-21 8:34 ` Petr Mladek
2022-10-31 13:06 ` John Ogness
2022-10-31 14:09 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 04/38] printk: introduce console_is_enabled() wrapper John Ogness
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-21 8:57 ` Petr Mladek
2022-10-21 9:37 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 05/38] printk: use console_is_enabled() John Ogness
2022-10-21 9:25 ` Petr Mladek
2022-10-31 15:39 ` John Ogness
2022-10-19 14:55 ` [PATCH printk v2 06/38] tty: nfcon: " John Ogness
2022-10-21 9:55 ` Petr Mladek
2022-10-31 15:59 ` John Ogness
2022-11-01 8:57 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 07/38] um: kmsg_dump: " John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-21 12:46 ` Petr Mladek
2022-10-21 12:46 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 08/38] efi: earlycon: " John Ogness
2022-10-19 15:32 ` Ard Biesheuvel
2022-10-21 12:53 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 09/38] netconsole: " John Ogness
2022-10-21 13:14 ` Petr Mladek
2022-11-04 15:12 ` John Ogness
2022-10-19 14:55 ` [PATCH printk v2 10/38] tty: hvc: " John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-21 13:22 ` Petr Mladek
2022-10-21 13:22 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 11/38] tty: serial: earlycon: " John Ogness
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-21 13:51 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 12/38] tty: serial: kgdboc: " John Ogness
2022-10-19 16:00 ` Greg Kroah-Hartman
2022-10-21 14:10 ` Petr Mladek
2022-10-24 22:46 ` Doug Anderson
2022-10-25 0:49 ` Doug Anderson
2022-10-25 11:28 ` John Ogness
2022-11-04 16:23 ` John Ogness
2022-11-07 8:47 ` Petr Mladek
2022-11-07 9:45 ` John Ogness
2022-10-19 14:55 ` [PATCH printk v2 13/38] tty: serial: pic32_uart: " John Ogness
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-21 14:11 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 14/38] tty: serial: samsung_tty: " John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-19 16:00 ` Greg Kroah-Hartman
2022-10-19 16:00 ` Greg Kroah-Hartman
2022-10-21 14:14 ` Petr Mladek
2022-10-21 14:14 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 15/38] tty: serial: serial_core: " John Ogness
2022-10-19 16:00 ` Greg Kroah-Hartman
2022-10-21 14:14 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 16/38] tty: serial: xilinx_uartps: " John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-21 14:23 ` Petr Mladek
2022-10-21 14:23 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 17/38] tty: tty_io: " John Ogness
2022-10-19 16:00 ` Greg Kroah-Hartman
2022-10-21 14:24 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 18/38] usb: early: xhci-dbc: " John Ogness
2022-10-19 16:01 ` Greg Kroah-Hartman
2022-10-21 14:27 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 19/38] kdb: kdb_io: " John Ogness
2022-10-21 14:28 ` Petr Mladek
2022-10-25 0:34 ` Doug Anderson
2022-10-19 14:55 ` [PATCH printk v2 20/38] um: kmsg_dumper: use srcu console list iterator John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-21 14:56 ` Petr Mladek
2022-10-21 14:56 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 21/38] serial: kgdboc: " John Ogness
2022-10-19 16:02 ` Greg Kroah-Hartman
2022-10-21 15:09 ` Petr Mladek
2022-10-25 0:33 ` Doug Anderson
2022-10-19 14:55 ` [PATCH printk v2 22/38] serial: kgdboc: document console_lock usage John Ogness
2022-10-20 7:42 ` Greg Kroah-Hartman
2022-10-25 0:36 ` Doug Anderson
2022-10-25 10:09 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 23/38] tty: tty_io: " John Ogness
2022-10-20 7:43 ` Greg Kroah-Hartman
2022-10-25 13:31 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 24/38] xen: fbfront: use srcu console list iterator John Ogness
2022-10-19 14:55 ` John Ogness
2022-10-25 13:39 ` Petr Mladek
2022-10-25 13:39 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 25/38] proc: consoles: document console_lock usage John Ogness
2022-10-25 14:40 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 26/38] kdb: use srcu console list iterator John Ogness
2022-10-25 0:47 ` Doug Anderson
2022-10-25 14:59 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 27/38] printk: console_flush_all: " John Ogness
2022-10-25 15:17 ` Petr Mladek
2022-11-07 0:00 ` John Ogness
2022-11-07 13:03 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 28/38] printk: console_unblank: " John Ogness
2022-10-25 15:28 ` Petr Mladek
2022-10-25 15:31 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 29/38] printk: console_flush_on_panic: " John Ogness
2022-10-25 15:32 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 30/38] printk: console_device: " John Ogness
2022-10-25 15:35 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 31/38] printk: register_console: " John Ogness
2022-10-26 8:20 ` Petr Mladek [this message]
2022-10-19 14:55 ` [PATCH printk v2 32/38] printk: __pr_flush: " John Ogness
2022-10-26 8:33 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 33/38] printk: introduce console_list_lock John Ogness
2022-10-20 7:53 ` Greg Kroah-Hartman
2022-10-27 10:09 ` Petr Mladek
2022-10-27 18:50 ` Paul E. McKenney
2022-10-28 18:09 ` Boqun Feng
2022-10-28 18:42 ` Paul E. McKenney
2022-11-07 10:10 ` John Ogness
2022-11-07 16:16 ` Paul E. McKenney
2022-10-19 14:55 ` [PATCH printk v2 34/38] serial: kgdboc: use console_list_lock instead of console_lock John Ogness
2022-10-20 7:52 ` Greg Kroah-Hartman
2022-10-27 10:13 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 35/38] tty: tty_io: use console_list_lock for list synchronization John Ogness
2022-10-20 7:43 ` Greg Kroah-Hartman
2022-10-27 10:17 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 36/38] proc: consoles: use console_list_lock for list iteration John Ogness
2022-10-27 12:02 ` Petr Mladek
2022-10-19 14:55 ` [PATCH printk v2 37/38] printk: relieve console_lock of list synchronization duties John Ogness
2022-10-27 12:40 ` Petr Mladek
2022-10-19 14:56 ` [PATCH printk v2 38/38] printk, xen: fbfront: create/use safe function for forcing preferred John Ogness
2022-10-19 14:56 ` John Ogness
2022-10-27 13:18 ` Petr Mladek
2022-10-27 13:18 ` Petr Mladek
2022-10-27 13:35 ` John Ogness
2022-10-27 13:35 ` John Ogness
2022-10-27 14:27 ` Petr Mladek
2022-10-27 14:27 ` Petr Mladek
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