From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, Helge Deller <deller@gmx.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Javier Martinez Canillas <javierm@redhat.com>,
Thomas Zimmermann <tzimmermann@suse.de>,
Juergen Gross <jgross@suse.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Tom Rix <trix@redhat.com>,
linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH printk v3 33/40] printk, xen: fbfront: create/use safe function for forcing preferred
Date: Thu, 10 Nov 2022 17:09:12 +0106 [thread overview]
Message-ID: <877d026blr.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <Y20aBwNWT19YDeib@alley>
On 2022-11-10, Petr Mladek <pmladek@suse.com> wrote:
>> +void console_force_preferred_locked(struct console *con)
>> +{
>> + struct console *cur_pref_con;
>> +
>> + if (!console_is_registered_locked(con))
>> + return;
>> +
>> + cur_pref_con = console_first();
>> +
>> + /* Already preferred? */
>> + if (cur_pref_con == con)
>> + return;
>> +
>> + hlist_del_init_rcu(&con->node);
>
> We actually should re-initialize the node only after all existing
> console list walks are finished. Se we should use here:
>
> hlist_del_rcu(&con->node);
hlist_del_init_rcu() only re-initializes @pprev pointer. But maybe you
are concerned that there is a window where list_unhashed() becomes true?
I agree that it should be changed to hlist_del_rcu() because there
should not be a window where this console appears unregistered.
>> + /* Only the new head can have CON_CONSDEV set. */
>> + WRITE_ONCE(cur_pref_con->flags, cur_pref_con->flags & ~CON_CONSDEV);
>
> As mentioned in the reply for 7th patch, I would prefer to hide this
> WRITE_ONCE into a wrapper, e.g. console_set_flag(). It might also
> check that the console_list_lock is taken...
Agreed. For v4 it will become:
console_srcu_write_flags(cur_pref_con->flags & ~CON_CONSDEV);
John
WARNING: multiple messages have this Message-ID (diff)
From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Juergen Gross <jgross@suse.com>,
linux-fbdev@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Helge Deller <deller@gmx.de>,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Javier Martinez Canillas <javierm@redhat.com>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
dri-devel@lists.freedesktop.org,
Thomas Zimmermann <tzimmermann@suse.de>,
Tom Rix <trix@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH printk v3 33/40] printk, xen: fbfront: create/use safe function for forcing preferred
Date: Thu, 10 Nov 2022 17:09:12 +0106 [thread overview]
Message-ID: <877d026blr.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <Y20aBwNWT19YDeib@alley>
On 2022-11-10, Petr Mladek <pmladek@suse.com> wrote:
>> +void console_force_preferred_locked(struct console *con)
>> +{
>> + struct console *cur_pref_con;
>> +
>> + if (!console_is_registered_locked(con))
>> + return;
>> +
>> + cur_pref_con = console_first();
>> +
>> + /* Already preferred? */
>> + if (cur_pref_con == con)
>> + return;
>> +
>> + hlist_del_init_rcu(&con->node);
>
> We actually should re-initialize the node only after all existing
> console list walks are finished. Se we should use here:
>
> hlist_del_rcu(&con->node);
hlist_del_init_rcu() only re-initializes @pprev pointer. But maybe you
are concerned that there is a window where list_unhashed() becomes true?
I agree that it should be changed to hlist_del_rcu() because there
should not be a window where this console appears unregistered.
>> + /* Only the new head can have CON_CONSDEV set. */
>> + WRITE_ONCE(cur_pref_con->flags, cur_pref_con->flags & ~CON_CONSDEV);
>
> As mentioned in the reply for 7th patch, I would prefer to hide this
> WRITE_ONCE into a wrapper, e.g. console_set_flag(). It might also
> check that the console_list_lock is taken...
Agreed. For v4 it will become:
console_srcu_write_flags(cur_pref_con->flags & ~CON_CONSDEV);
John
next prev parent reply other threads:[~2022-11-10 16:03 UTC|newest]
Thread overview: 129+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-07 14:15 [PATCH printk v3 00/40] reduce console_lock scope John Ogness
2022-11-07 14:15 ` John Ogness
2022-11-07 14:15 ` John Ogness
2022-11-07 14:15 ` John Ogness
2022-11-07 14:15 ` [PATCH printk v3 01/40] rcu: implement lockdep_rcu_enabled for !CONFIG_DEBUG_LOCK_ALLOC John Ogness
2022-11-07 18:01 ` Paul E. McKenney
2022-11-07 19:23 ` John Ogness
2022-11-08 19:27 ` Paul E. McKenney
2022-11-09 17:49 ` Paul E. McKenney
2022-11-08 10:29 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 02/40] serial: kgdboc: Lock console list in probe function John Ogness
2022-11-09 8:20 ` Daniel Thompson
2022-11-07 14:16 ` [PATCH printk v3 03/40] printk: Convert console_drivers list to hlist John Ogness
2022-11-07 14:16 ` [PATCH printk v3 04/40] printk: Prepare for SRCU console list protection John Ogness
2022-11-08 12:14 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 05/40] printk: fix setting first seq for consoles John Ogness
2022-11-08 12:20 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 06/40] um: kmsg_dump: only dump when no output console available John Ogness
2022-11-07 14:16 ` John Ogness
2022-11-08 12:41 ` Petr Mladek
2022-11-08 12:41 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 07/40] console: introduce console_is_enabled() wrapper John Ogness
2022-11-08 16:18 ` Petr Mladek
2022-11-10 15:05 ` John Ogness
2022-11-11 13:32 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 08/40] printk: use console_is_enabled() John Ogness
2022-11-08 17:40 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 09/40] um: kmsg_dump: " John Ogness
2022-11-07 14:16 ` John Ogness
2022-11-09 14:52 ` Petr Mladek
2022-11-09 14:52 ` Petr Mladek
2022-11-09 14:56 ` Petr Mladek
2022-11-09 14:56 ` Petr Mladek
2022-11-09 14:57 ` Petr Mladek
2022-11-09 14:57 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 10/40] kdb: kdb_io: " John Ogness
2022-11-09 8:22 ` Daniel Thompson
2022-11-09 14:59 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 11/40] um: kmsg_dumper: use srcu console list iterator John Ogness
2022-11-07 14:16 ` John Ogness
2022-11-09 15:05 ` Petr Mladek
2022-11-09 15:05 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 12/40] tty: serial: kgdboc: document console_lock usage John Ogness
2022-11-09 8:23 ` Daniel Thompson
2022-11-09 15:19 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 13/40] tty: tty_io: " John Ogness
2022-11-09 15:20 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 14/40] proc: consoles: " John Ogness
2022-11-09 15:22 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 15/40] kdb: use srcu console list iterator John Ogness
2022-11-09 8:53 ` Daniel Thompson
2022-11-09 9:27 ` John Ogness
2022-11-09 15:27 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 16/40] printk: console_flush_all: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 17/40] printk: console_unblank: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 18/40] printk: console_flush_on_panic: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 19/40] printk: console_device: " John Ogness
2022-11-09 15:58 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 20/40] printk: __pr_flush: " John Ogness
2022-11-07 14:16 ` [PATCH printk v3 21/40] printk: introduce console_list_lock John Ogness
2022-11-10 12:58 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 22/40] console: introduce console_is_registered() John Ogness
2022-11-10 13:00 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 23/40] serial_core: replace uart_console_enabled() with uart_console_registered() John Ogness
2022-11-08 8:46 ` Geert Uytterhoeven
2022-11-10 13:24 ` Petr Mladek
2022-11-10 13:46 ` John Ogness
2022-11-07 14:16 ` [PATCH printk v3 24/40] tty: nfcon: use console_is_registered() John Ogness
2022-11-08 8:39 ` Geert Uytterhoeven
2022-11-10 13:58 ` Petr Mladek
2022-11-10 14:19 ` John Ogness
2022-11-10 17:50 ` Eero Tamminen
2022-11-07 14:16 ` [PATCH printk v3 25/40] efi: earlycon: " John Ogness
2022-11-10 14:28 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 26/40] tty: hvc: " John Ogness
2022-11-07 14:16 ` John Ogness
2022-11-10 14:52 ` Petr Mladek
2022-11-10 14:52 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 27/40] tty: serial: earlycon: " John Ogness
2022-11-10 15:00 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 28/40] tty: serial: pic32_uart: " John Ogness
2022-11-10 15:01 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 29/40] tty: serial: samsung_tty: " John Ogness
2022-11-07 14:16 ` John Ogness
2022-11-10 15:01 ` Petr Mladek
2022-11-10 15:01 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 30/40] tty: serial: xilinx_uartps: " John Ogness
2022-11-07 14:16 ` John Ogness
2022-11-10 15:04 ` Petr Mladek
2022-11-10 15:04 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 31/40] usb: early: xhci-dbc: " John Ogness
2022-11-10 15:05 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 32/40] netconsole: avoid CON_ENABLED misuse to track registration John Ogness
2022-11-10 15:17 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 33/40] printk, xen: fbfront: create/use safe function for forcing preferred John Ogness
2022-11-07 14:16 ` John Ogness
2022-11-10 15:34 ` Petr Mladek
2022-11-10 15:34 ` Petr Mladek
2022-11-10 16:03 ` John Ogness [this message]
2022-11-10 16:03 ` John Ogness
2022-11-10 17:26 ` Petr Mladek
2022-11-10 17:26 ` Petr Mladek
2022-11-10 22:37 ` John Ogness
2022-11-10 22:37 ` John Ogness
2022-11-11 10:48 ` Petr Mladek
2022-11-11 10:48 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 34/40] tty: tty_io: use console_list_lock for list synchronization John Ogness
2022-11-07 14:16 ` [PATCH printk v3 35/40] proc: consoles: use console_list_lock for list iteration John Ogness
2022-11-07 14:16 ` [PATCH printk v3 36/40] tty: serial: kgdboc: use console_list_lock for list traversal John Ogness
2022-11-09 9:06 ` Daniel Thompson
2022-11-09 9:44 ` John Ogness
2022-11-10 18:00 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 37/40] tty: serial: kgdboc: synchronize tty_find_polling_driver() and register_console() John Ogness
2022-11-10 15:13 ` Daniel Thompson
2022-11-10 18:03 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 38/40] tty: serial: kgdboc: use console_list_lock to trap exit John Ogness
2022-11-10 15:18 ` Daniel Thompson
2022-11-11 9:59 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 39/40] printk: relieve console_lock of list synchronization duties John Ogness
2022-11-07 16:30 ` John Ogness
2022-11-11 10:27 ` Petr Mladek
2022-11-11 13:06 ` Petr Mladek
2022-11-07 14:16 ` [PATCH printk v3 40/40] tty: serial: sh-sci: use setup() callback for early console John Ogness
2022-11-08 8:53 ` Geert Uytterhoeven
2022-11-11 17:15 ` Petr Mladek
2022-11-11 14:43 ` [PATCH printk v3 00/40] reduce console_lock scope Mathieu Desnoyers
2022-11-11 14:43 ` Mathieu Desnoyers
2022-11-11 14:43 ` Mathieu Desnoyers
2022-11-11 14:43 ` Mathieu Desnoyers
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