From: Petr Mladek <pmladek@suse•com>
To: Marcos Paulo de Souza <mpdesouza@suse•com>
Cc: Richard Weinberger <richard@nod•at>,
Anton Ivanov <anton.ivanov@cambridgegreys•com>,
Johannes Berg <johannes@sipsolutions•net>,
Greg Kroah-Hartman <gregkh@linuxfoundation•org>,
Jason Wessel <jason.wessel@windriver•com>,
Daniel Thompson <danielt@kernel•org>,
Douglas Anderson <dianders@chromium•org>,
Steven Rostedt <rostedt@goodmis•org>,
John Ogness <john.ogness@linutronix•de>,
Sergey Senozhatsky <senozhatsky@chromium•org>,
Jiri Slaby <jirislaby@kernel•org>,
Breno Leitao <leitao@debian•org>,
Andrew Lunn <andrew+netdev@lunn•ch>,
"David S. Miller" <davem@davemloft•net>,
Eric Dumazet <edumazet@google•com>,
Jakub Kicinski <kuba@kernel•org>, Paolo Abeni <pabeni@redhat•com>,
Geert Uytterhoeven <geert@linux-m68k•org>,
Kees Cook <kees@kernel•org>, Tony Luck <tony.luck@intel•com>,
"Guilherme G. Piccoli" <gpiccoli@igalia•com>,
Madhavan Srinivasan <maddy@linux•ibm.com>,
Michael Ellerman <mpe@ellerman•id.au>,
Nicholas Piggin <npiggin@gmail•com>,
Christophe Leroy <christophe.leroy@csgroup•eu>,
Andreas Larsson <andreas@gaisler•com>,
Alexander Shishkin <alexander.shishkin@linux•intel.com>,
Maxime Coquelin <mcoquelin.stm32@gmail•com>,
Alexandre Torgue <alexandre.torgue@foss•st.com>,
Jacky Huang <ychuang3@nuvoton•com>,
Shan-Chun Hung <schung@nuvoton•com>,
Laurentiu Tudor <laurentiu.tudor@nxp•com>,
linux-um@lists•infradead.org, linux-kernel@vger•kernel.org,
kgdb-bugreport@lists•sourceforge.net,
linux-serial@vger•kernel.org, netdev@vger•kernel.org,
linux-m68k@lists•linux-m68k.org, linux-hardening@vger•kernel.org,
linuxppc-dev@lists•ozlabs.org, sparclinux@vger•kernel.org,
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linux-arm-kernel@lists•infradead.org,
linux-fsdevel@vger•kernel.org
Subject: Re: [PATCH 04/19] printk: Reintroduce consoles_suspended global state
Date: Wed, 14 Jan 2026 14:12:18 +0100 [thread overview]
Message-ID: <aWeWMga1VaT0sYwj@pathway.suse.cz> (raw)
In-Reply-To: <20251227-printk-cleanup-part3-v1-4-21a291bcf197@suse.com>
On Sat 2025-12-27 09:16:11, Marcos Paulo de Souza wrote:
> This change partially reverts commit 9e70a5e109a4
> ("printk: Add per-console suspended state"). The intent of the original
> commit was to move the management of the console suspended state to the
> consoles themselves to be able to use SRCU instead of console lock.
>
> But having a global state is still useful when checking if the global
> suspend was triggered by power management. This way, instead of setting
> the state of each individual console, the code would only set/read from the
> global state.
>
> Along with this change, two more fixes are necessary: change
> console_{suspend,resume} to set/clear CON_SUSPEND instead of setting
> CON_ENABLED and change show_cons_active to call __console_is_usable to
> check console usefulness.
I would invert the logic a bit. I think that the main motivation
is to replace CON_ENABLE -> CON_SUSPEND.
<proposal>
The flag CON_ENABLE is cleared when serial drivers get suspended. This
"hack" has been added by the commit 33c0d1b0c3ebb6 ("[PATCH] Serial
driver stuff") back in v2.5.28.
Stop hijacking CON_ENABLE flag and use the CON_SUSPEND flag instead.
Still allow to distinguish when:
- the backing device is being suspended, see console_suspend().
- the power management wants to calm down all consoles using
a big-hammer, see console_suspend_all().
And restore the global "consoles_suspended" flag which was removed
by the commit 9e70a5e109a4 ("printk: Add per-console suspended state").
The difference is that accesses to the new global flag are
synchronized the same way as to the CON_SUSPEND flag. It allows
to read it under console_srcu_read_lock().
Finally, use __console_is_usable() in show_cons_active(). It is the
last location where the CON_ENABLED flag was checked directly.
The patch should not change the existing behavior because all users check
the state of the console using console_is_usable().
</proposal>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index e2d92cf70eb7..7d2bded75b75 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -3552,9 +3552,9 @@ static ssize_t show_cons_active(struct device *dev,
> for_each_console(c) {
> if (!c->device)
> continue;
> - if (!(c->flags & CON_NBCON) && !c->write)
> - continue;
> - if ((c->flags & CON_ENABLED) == 0)
> + if (!__console_is_usable(c, c->flags,
> + consoles_suspended,
> + NBCON_USE_ANY))
It would be better to move this into a separate patch.
> continue;
> cs[i++] = c;
> if (i >= ARRAY_SIZE(cs))
Otherwise, it looks good.
Best Regards,
Petr
next prev parent reply other threads:[~2026-01-14 13:12 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-27 12:16 [PATCH 00/19] printk cleanup - part 3 Marcos Paulo de Souza
2025-12-27 12:16 ` [PATCH 01/19] printk/nbcon: Use an enum to specify the required callback in console_is_usable() Marcos Paulo de Souza
2026-01-13 16:25 ` Petr Mladek
2026-01-30 15:31 ` John Ogness
2025-12-27 12:16 ` [PATCH 02/19] printk: Introduce console_is_nbcon Marcos Paulo de Souza
2026-01-13 17:37 ` Petr Mladek
2026-01-30 15:50 ` John Ogness
2025-12-27 12:16 ` [PATCH 03/19] printk: Drop flags argument from console_is_usable Marcos Paulo de Souza
2026-01-14 8:44 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 04/19] printk: Reintroduce consoles_suspended global state Marcos Paulo de Souza
2026-01-14 13:12 ` Petr Mladek [this message]
2025-12-27 12:16 ` [PATCH 05/19] printk: Add more context to suspend/resume functions Marcos Paulo de Souza
2026-01-14 13:20 ` Petr Mladek
2026-01-30 17:27 ` John Ogness
2025-12-27 12:16 ` [PATCH 06/19] printk: Introduce register_console_force Marcos Paulo de Souza
2026-01-14 14:22 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 07/19] drivers: netconsole: Migrate to register_console_force helper Marcos Paulo de Souza
2026-01-15 10:16 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 08/19] debug: debug_core: " Marcos Paulo de Souza
2026-01-15 10:20 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 09/19] m68k: emu: nfcon.c: " Marcos Paulo de Souza
2026-01-15 10:26 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 10/19] fs: pstore: platform: " Marcos Paulo de Souza
2026-01-15 11:05 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 11/19] powerpc: kernel: udbg: " Marcos Paulo de Souza
2026-01-15 12:13 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 12/19] sparc: kernel: btext: " Marcos Paulo de Souza
2026-01-15 12:14 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 13/19] um: drivers: mconsole_kern.c: " Marcos Paulo de Souza
2026-01-15 12:24 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 14/19] drivers: hwtracing: stm: console.c: " Marcos Paulo de Souza
2026-01-15 12:29 ` Petr Mladek
2026-01-16 13:04 ` Alexander Shishkin
2026-01-16 13:54 ` Marcos Paulo de Souza
2025-12-27 12:16 ` [PATCH 15/19] drivers: tty: serial: mux.c: " Marcos Paulo de Souza
2026-01-16 9:59 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 16/19] drivers: tty: serial: ma35d1_serial: " Marcos Paulo de Souza
2026-01-15 16:28 ` Petr Mladek
2025-12-27 12:16 ` [PATCH 17/19] drivers: tty: ehv_bytechan: " Marcos Paulo de Souza
2025-12-27 12:16 ` [PATCH 18/19] drivers: braille: console: Drop CON_ENABLED console flag Marcos Paulo de Souza
2025-12-27 12:16 ` [PATCH 19/19] printk: Remove CON_ENABLED flag Marcos Paulo de Souza
2026-01-05 12:52 ` [PATCH 00/19] printk cleanup - part 3 Daniel Thompson
2026-01-05 14:08 ` Daniel Thompson
2026-01-13 12:41 ` Marcos Paulo de Souza
2026-01-14 0:32 ` Marcos Paulo de Souza
2026-01-14 8:20 ` Petr Mladek
2026-01-14 16:38 ` Daniel Thompson
2026-01-07 10:22 ` Andreas Larsson
2026-01-12 17:53 ` Marcos Paulo de Souza
2026-02-20 11:43 ` Marcos Paulo de Souza
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