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From: Anna-Maria Behnsen <anna-maria@linutronix.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linuxfoundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Stephen Boyd <sboyd@kernel.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Julia Lawall <Julia.Lawall@inria.fr>,
	Arnd Bergmann <arnd@arndb.de>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Marc Zyngier <maz@kernel.org>,
	Marcel Holtmann <marcel@holtmann.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	linux-bluetooth@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	netdev@vger.kernel.org
Subject: Re: [patch V2 12/17] timers: Silently ignore timers with a NULL function
Date: Wed, 23 Nov 2022 10:22:08 +0100 (CET)	[thread overview]
Message-ID: <ce3f4736-33de-a6bd-6e86-567bec097bf@linutronix.de> (raw)
In-Reply-To: <20221122173648.793640919@linutronix.de>

On Tue, 22 Nov 2022, Thomas Gleixner wrote:

> Tearing down timers which have circular dependencies to other
> functionality, e.g. workqueues, where the timer can schedule work and work
> can arm timers is not trivial.

NIT (comma is missing): can arm timer, is not trivial.

> In those cases it is desired to shutdown the timer in a way which prevents
> rearming of the timer. The mechanism to do so it to set timer->function to

s/to do so it/to do so is/

> NULL and use this as an indicator for the timer arming functions to ignore
> the (re)arm request.
> 
> In preparation for that replace the warnings in the relevant code pathes
> with checks for timer->function == NULL and discard the rearm request
> silently.

Here is a verb missing that this is a grammatically correct (and
understandable) sentence.

> Add debug_assert_init() instead of the WARN_ON_ONCE(!timer->function)
> checks so that debug objects can warn about non-initialized timers.
> 
> If developers fail to enable debug objects and then waste lots of time to
> figure out why their non-initialized timer is not firing, they deserve it.
> 
> Co-developed-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Guenter Roeck <linux@roeck-us.net>
> Link: https://lore.kernel.org/all/20220407161745.7d6754b3@gandalf.local.home
> Link: https://lore.kernel.org/all/20221110064101.429013735@goodmis.org
> ---
> V2: Use continue instead of return and amend the return value docs (Steven)
> ---
>  kernel/time/timer.c |   60 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 55 insertions(+), 5 deletions(-)
> 
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -1128,8 +1144,12 @@ static inline int
>   * mod_timer_pending() is the same for pending timers as mod_timer(), but
>   * will not activate inactive timers.
>   *
> + * If @timer->function == NULL then the start operation is silently
> + * discarded.
> + *
>   * Return:
> - * * %0 - The timer was inactive and not modified
> + * * %0 - The timer was inactive and not modified or was is in
> + *	  shutdown state and the operation was discarded

Do you mean "was" or "is"? Please have also a look at the places where you
use the same phrase.

>   * * %1 - The timer was active and requeued to expire at @expires
>   */
>  int mod_timer_pending(struct timer_list *timer, unsigned long expires)
> @@ -1155,8 +1175,12 @@ EXPORT_SYMBOL(mod_timer_pending);
>   * same timer, then mod_timer() is the only safe way to modify the timeout,
>   * since add_timer() cannot modify an already running timer.
>   *
> + * If @timer->function == NULL then the start operation is silently
> + * discarded, the return value is 0 and meaningless.

It's easier to read, if you make a dot instead of comma.


Thanks,

	Anna-Maria

  reply	other threads:[~2022-11-23  9:23 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-22 17:44 [patch V2 00/17] timers: Provide timer_shutdown[_sync]() Thomas Gleixner
2022-11-22 17:44 ` [patch V2 01/17] Documentation: Remove bogus claim about del_timer_sync() Thomas Gleixner
2022-11-22 18:37   ` timers: Provide timer_shutdown[_sync]() bluez.test.bot
2022-11-22 17:44 ` [patch V2 02/17] ARM: spear: Do not use timer namespace for timer_shutdown() function Thomas Gleixner
2022-11-22 17:44 ` [patch V2 03/17] clocksource/drivers/arm_arch_timer: " Thomas Gleixner
2022-11-22 17:44 ` [patch V2 04/17] clocksource/drivers/sp804: " Thomas Gleixner
2022-11-22 17:44 ` [patch V2 05/17] timers: Get rid of del_singleshot_timer_sync() Thomas Gleixner
2022-11-22 17:44 ` [patch V2 06/17] timers: Replace BUG_ON()s Thomas Gleixner
2022-11-22 17:44 ` [patch V2 07/17] timers: Update kernel-doc for various functions Thomas Gleixner
2022-11-23 10:23   ` Anna-Maria Behnsen
2022-11-23 17:09     ` Thomas Gleixner
2022-11-22 17:44 ` [patch V2 08/17] timers: Use del_timer_sync() even on UP Thomas Gleixner
2022-11-22 17:44 ` [patch V2 09/17] timers: Rename del_timer_sync() to timer_delete_sync() Thomas Gleixner
2022-11-22 22:23   ` David Laight
2022-11-22 22:45     ` Steven Rostedt
2022-11-23  0:08       ` Thomas Gleixner
2022-11-23  0:28         ` Steven Rostedt
2022-11-22 17:45 ` [patch V2 10/17] timers: Rename del_timer() to timer_delete() Thomas Gleixner
2022-11-22 17:45 ` [patch V2 11/17] Documentation: Replace del_timer/del_timer_sync() Thomas Gleixner
2022-11-22 17:45 ` [patch V2 12/17] timers: Silently ignore timers with a NULL function Thomas Gleixner
2022-11-23  9:22   ` Anna-Maria Behnsen [this message]
2022-11-23 10:39   ` Anna-Maria Behnsen
2022-11-23 11:06   ` Anna-Maria Behnsen
2022-11-23 17:08     ` Thomas Gleixner
2022-11-22 17:45 ` [patch V2 13/17] timers: Split [try_to_]del_timer[_sync]() to prepare for shutdown mode Thomas Gleixner
2022-11-22 23:04   ` Jacob Keller
2022-11-23 17:05     ` Thomas Gleixner
2022-11-23 18:45       ` Jacob Keller
2022-11-23 11:23   ` Anna-Maria Behnsen
2022-11-23 11:24     ` Anna-Maria Behnsen
2022-11-22 17:45 ` [patch V2 14/17] timers: Add shutdown mechanism to the internal functions Thomas Gleixner
2022-11-22 17:45 ` [patch V2 15/17] timers: Provide timer_shutdown[_sync]() Thomas Gleixner
2022-11-23 12:02   ` Anna-Maria Behnsen
2022-11-23 17:06     ` Thomas Gleixner
2022-11-22 17:45 ` [patch V2 16/17] timers: Update the documentation to reflect on the new timer_shutdown() API Thomas Gleixner
2022-11-22 17:45 ` [patch V2 17/17] Bluetooth: hci_qca: Fix the teardown problem for real Thomas Gleixner
2022-11-22 23:09 ` [patch V2 00/17] timers: Provide timer_shutdown[_sync]() Jacob Keller

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