[PATCH v2 00/15] timers: Cleanup delay/sleep related mess

[PATCH v2 00/15] timers: Cleanup delay/sleep related mess

[Anna-Maria Behnsen]

Hi,

a question about which sleeping function should be used in acpi_os_sleep()
started a discussion and examination about the existing documentation and
implementation of functions which insert a sleep/delay.

The result of the discussion was, that the documentation is outdated and
the implemented fsleep() reflects the outdated documentation but doesn't
help to reflect reality which in turns leads to the queue which covers the
following things:

- Split out all timeout and sleep related functions from hrtimer.c and timer.c
  into a separate file

- Update function descriptions of sleep related functions

- Change fsleep() to reflect reality

- Rework all comments or users which obviously rely on the outdated
  documentation as they reference "Documentation/timers/timers-howto.rst"

- Last but not least (as there are no more references): Update the outdated
  documentation and move it into a file with a self explaining file name

The queue is available here and applies on top of tip/timers/core:

  git://git.kernel.org/pub/scm/linux/kernel/git/anna-maria/linux-devel.git timers/misc

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
Changes in v2:
- change udelay() and ndelay() as suggested by Thomas
- Update some formatting in the new sleep_timeout.c file
- minor typo changes and other small review remarks

Thanks,

        Anna-Maria

---
Anna-Maria Behnsen (15):
      MAINTAINERS: Add missing file include/linux/delay.h
      timers: Move *sleep*() and timeout functions into a separate file
      timers: Update schedule_[hr]timeout*() related function descriptions
      timers: Rename usleep_idle_range() to usleep_range_idle()
      timers: Update function descriptions of sleep/delay related functions
      delay: Rework udelay and ndelay
      timers: Adjust flseep() to reflect reality
      mm/damon/core: Use generic upper bound recommondation for usleep_range()
      timers: Add a warning to usleep_range_state() for wrong order of arguments
      checkpatch: Remove broken sleep/delay related checks
      regulator: core: Use fsleep() to get best sleep mechanism
      iopoll/regmap/phy/snd: Fix comment referencing outdated timer documentation
      powerpc/rtas: Use fsleep() to minimize additional sleep duration
      media: anysee: Fix link to outdated sleep function documentation
      timers/Documentation: Cleanup delay/sleep documentation

 Documentation/dev-tools/checkpatch.rst         |   6 -
 Documentation/timers/delay_sleep_functions.rst | 122 ++++++++
 Documentation/timers/index.rst                 |   2 +-
 Documentation/timers/timers-howto.rst          | 115 --------
 MAINTAINERS                                    |   2 +
 arch/powerpc/kernel/rtas.c                     |  21 +-
 drivers/media/usb/dvb-usb-v2/anysee.c          |   6 +-
 drivers/regulator/core.c                       |  47 +---
 include/asm-generic/delay.h                    |  95 +++++--
 include/linux/delay.h                          |  79 ++++--
 include/linux/iopoll.h                         |  52 ++--
 include/linux/phy.h                            |   9 +-
 include/linux/regmap.h                         |  38 +--
 kernel/time/Makefile                           |   2 +-
 kernel/time/hrtimer.c                          | 120 --------
 kernel/time/sleep_timeout.c                    | 376 +++++++++++++++++++++++++
 kernel/time/timer.c                            | 192 -------------
 mm/damon/core.c                                |   5 +-
 scripts/checkpatch.pl                          |  38 ---
 sound/soc/sof/ops.h                            |   8 +-
 20 files changed, 701 insertions(+), 634 deletions(-)

[PATCH v2 14/15] media: anysee: Fix link to outdated sleep function documentation

[Anna-Maria Behnsen]

The TODO FIXME comment references the outdated lower limit for msleep()
function of 20ms. As this is not right and the proper documentation of
msleep() is now part of the function description, remove the old stuff and
point to the up to date documentation.

Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-media@vger.kernel.org
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
 drivers/media/usb/dvb-usb-v2/anysee.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/anysee.c b/drivers/media/usb/dvb-usb-v2/anysee.c
index 8699846eb416..b2f5db961245 100644
--- a/drivers/media/usb/dvb-usb-v2/anysee.c
+++ b/drivers/media/usb/dvb-usb-v2/anysee.c
@@ -55,10 +55,8 @@ static int anysee_ctrl_msg(struct dvb_usb_device *d,
 
 	/* TODO FIXME: dvb_usb_generic_rw() fails rarely with error code -32
 	 * (EPIPE, Broken pipe). Function supports currently msleep() as a
-	 * parameter but I would not like to use it, since according to
-	 * Documentation/timers/timers-howto.rst it should not be used such
-	 * short, under < 20ms, sleeps. Repeating failed message would be
-	 * better choice as not to add unwanted delays...
+	 * parameter. Check msleep() for details. Repeating failed message would
+	 * be better choice as not to add unwanted delays...
 	 * Fixing that correctly is one of those or both;
 	 * 1) use repeat if possible
 	 * 2) add suitable delay

-- 
2.39.2

Re: [PATCH v2 00/15] timers: Cleanup delay/sleep related mess

[Christophe JAILLET]

Le 11/09/2024 à 07:13, Anna-Maria Behnsen a écrit :
> Hi,
> 
> a question about which sleeping function should be used in acpi_os_sleep()
> started a discussion and examination about the existing documentation and
> implementation of functions which insert a sleep/delay.
> 
> The result of the discussion was, that the documentation is outdated and
> the implemented fsleep() reflects the outdated documentation but doesn't
> help to reflect reality which in turns leads to the queue which covers the
> following things:
> 
> - Split out all timeout and sleep related functions from hrtimer.c and timer.c
>    into a separate file
> 
> - Update function descriptions of sleep related functions
> 
> - Change fsleep() to reflect reality
> 
> - Rework all comments or users which obviously rely on the outdated
>    documentation as they reference "Documentation/timers/timers-howto.rst"
> 
> - Last but not least (as there are no more references): Update the outdated
>    documentation and move it into a file with a self explaining file name
> 
> The queue is available here and applies on top of tip/timers/core:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/anna-maria/linux-devel.git timers/misc
> 
> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>

Hi,

not directly related to your serie, but some time ago I sent a patch to 
micro-optimize Optimize usleep_range(). (See [1])

The idea is that the 2 parameters of usleep_range() are usually 
constants and some code reordering could easily let the compiler compute 
a few things at compilation time.

There was consensus on the value of the change (see [2]), but as you are 
touching things here, maybe it makes sense now to save a few cycles at 
runtime and a few bytes of code?

CJ

[1]: 
https://lore.kernel.org/all/f0361b83a0a0b549f8ec5ab8134905001a6f2509.1659126514.git.christophe.jaillet@wanadoo.fr/

[2]: 
https://lore.kernel.org/all/03c2bbe795fe4ddcab66eb852bae3715@AcuMS.aculab.com/

Re: [PATCH v2 00/15] timers: Cleanup delay/sleep related mess

[Christophe JAILLET]

Le 16/09/2024 à 22:20, Christophe JAILLET a écrit :
> Le 11/09/2024 à 07:13, Anna-Maria Behnsen a écrit :
>> Hi,
>>
>> a question about which sleeping function should be used in 
>> acpi_os_sleep()
>> started a discussion and examination about the existing documentation and
>> implementation of functions which insert a sleep/delay.
>>
>> The result of the discussion was, that the documentation is outdated and
>> the implemented fsleep() reflects the outdated documentation but doesn't
>> help to reflect reality which in turns leads to the queue which covers 
>> the
>> following things:
>>
>> - Split out all timeout and sleep related functions from hrtimer.c and 
>> timer.c
>>    into a separate file
>>
>> - Update function descriptions of sleep related functions
>>
>> - Change fsleep() to reflect reality
>>
>> - Rework all comments or users which obviously rely on the outdated
>>    documentation as they reference "Documentation/timers/timers- 
>> howto.rst"
>>
>> - Last but not least (as there are no more references): Update the 
>> outdated
>>    documentation and move it into a file with a self explaining file name
>>
>> The queue is available here and applies on top of tip/timers/core:
>>
>>    git://git.kernel.org/pub/scm/linux/kernel/git/anna-maria/linux- 
>> devel.git timers/misc
>>
>> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
> 
> Hi,
> 
> not directly related to your serie, but some time ago I sent a patch to 
> micro-optimize Optimize usleep_range(). (See [1])
> 
> The idea is that the 2 parameters of usleep_range() are usually 
> constants and some code reordering could easily let the compiler compute 
> a few things at compilation time.
> 
> There was consensus on the value of the change (see [2]), but as you are 

Typo: there was *no* consensus...

> touching things here, maybe it makes sense now to save a few cycles at 
> runtime and a few bytes of code?
> 
> CJ
> 
> [1]: https://lore.kernel.org/all/ 
> f0361b83a0a0b549f8ec5ab8134905001a6f2509.1659126514.git.christophe.jaillet@wanadoo.fr/
> 
> [2]: https://lore.kernel.org/ 
> all/03c2bbe795fe4ddcab66eb852bae3715@AcuMS.aculab.com/
> 
> 
> 
> 

Re: [PATCH v2 00/15] timers: Cleanup delay/sleep related mess

[Anna-Maria Behnsen]

Christophe JAILLET <christophe.jaillet@wanadoo.fr> writes:

> Le 16/09/2024 à 22:20, Christophe JAILLET a écrit :
>> Le 11/09/2024 à 07:13, Anna-Maria Behnsen a écrit :
>>> Hi,
>>>
>>> a question about which sleeping function should be used in 
>>> acpi_os_sleep()
>>> started a discussion and examination about the existing documentation and
>>> implementation of functions which insert a sleep/delay.
>>>
>>> The result of the discussion was, that the documentation is outdated and
>>> the implemented fsleep() reflects the outdated documentation but doesn't
>>> help to reflect reality which in turns leads to the queue which covers 
>>> the
>>> following things:
>>>
>>> - Split out all timeout and sleep related functions from hrtimer.c and 
>>> timer.c
>>>    into a separate file
>>>
>>> - Update function descriptions of sleep related functions
>>>
>>> - Change fsleep() to reflect reality
>>>
>>> - Rework all comments or users which obviously rely on the outdated
>>>    documentation as they reference "Documentation/timers/timers- 
>>> howto.rst"
>>>
>>> - Last but not least (as there are no more references): Update the 
>>> outdated
>>>    documentation and move it into a file with a self explaining file name
>>>
>>> The queue is available here and applies on top of tip/timers/core:
>>>
>>>    git://git.kernel.org/pub/scm/linux/kernel/git/anna-maria/linux- 
>>> devel.git timers/misc
>>>
>>> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
>> 
>> Hi,
>> 
>> not directly related to your serie, but some time ago I sent a patch to 
>> micro-optimize Optimize usleep_range(). (See [1])
>> 
>> The idea is that the 2 parameters of usleep_range() are usually 
>> constants and some code reordering could easily let the compiler compute 
>> a few things at compilation time.
>> 
>> There was consensus on the value of the change (see [2]), but as you are 
>
> Typo: there was *no* consensus...
>
>> touching things here, maybe it makes sense now to save a few cycles at 
>> runtime and a few bytes of code?
>> 

Sorry for the late reply. I'll check it and will come back to you.

Thanks,
	Anna-Maria

Re: [PATCH v2 00/15] timers: Cleanup delay/sleep related mess

[Thomas Gleixner]

On Mon, Sep 16 2024 at 22:20, Christophe JAILLET wrote:
> Le 11/09/2024 à 07:13, Anna-Maria Behnsen a écrit :
>
> not directly related to your serie, but some time ago I sent a patch to 
> micro-optimize Optimize usleep_range(). (See [1])
>
> The idea is that the 2 parameters of usleep_range() are usually 
> constants and some code reordering could easily let the compiler compute 
> a few things at compilation time.
>
> There was consensus on the value of the change (see [2]), but as you are 
> touching things here, maybe it makes sense now to save a few cycles at 
> runtime and a few bytes of code?

For the price of yet another ugly interface and pushing the
multiplication into the non-constant call sites.

Seriously usleep() is not a hotpath operation and the multiplication is
not even measurable except in micro benchmarks.

Thanks,

        tglx

Re: [PATCH v2 14/15] media: anysee: Fix link to outdated sleep function documentation

[Frederic Weisbecker]

Le Wed, Sep 11, 2024 at 07:13:40AM +0200, Anna-Maria Behnsen a écrit :
> The TODO FIXME comment references the outdated lower limit for msleep()
> function of 20ms. As this is not right and the proper documentation of
> msleep() is now part of the function description, remove the old stuff and
> point to the up to date documentation.
> 
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: linux-media@vger.kernel.org
> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
> ---
>  drivers/media/usb/dvb-usb-v2/anysee.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb-v2/anysee.c b/drivers/media/usb/dvb-usb-v2/anysee.c
> index 8699846eb416..b2f5db961245 100644
> --- a/drivers/media/usb/dvb-usb-v2/anysee.c
> +++ b/drivers/media/usb/dvb-usb-v2/anysee.c
> @@ -55,10 +55,8 @@ static int anysee_ctrl_msg(struct dvb_usb_device *d,
>  
>  	/* TODO FIXME: dvb_usb_generic_rw() fails rarely with error code -32
>  	 * (EPIPE, Broken pipe). Function supports currently msleep() as a
> -	 * parameter but I would not like to use it, since according to
> -	 * Documentation/timers/timers-howto.rst it should not be used such
> -	 * short, under < 20ms, sleeps. Repeating failed message would be
> -	 * better choice as not to add unwanted delays...
> +	 * parameter. Check msleep() for details. Repeating failed message would
> +	 * be better choice as not to add unwanted delays...

Does the comment still matches any up-to-date worry? It passes 2000 ms which is
2 seconds...

Thanks.

>  	 * Fixing that correctly is one of those or both;
>  	 * 1) use repeat if possible
>  	 * 2) add suitable delay
> 
> -- 
> 2.39.2
> 

Re: [PATCH v2 14/15] media: anysee: Fix link to outdated sleep function documentation

[Anna-Maria Behnsen]

Frederic Weisbecker <frederic@kernel.org> writes:

> Le Wed, Sep 11, 2024 at 07:13:40AM +0200, Anna-Maria Behnsen a écrit :
>> The TODO FIXME comment references the outdated lower limit for msleep()
>> function of 20ms. As this is not right and the proper documentation of
>> msleep() is now part of the function description, remove the old stuff and
>> point to the up to date documentation.
>> 
>> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
>> Cc: linux-media@vger.kernel.org
>> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
>> ---
>>  drivers/media/usb/dvb-usb-v2/anysee.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/media/usb/dvb-usb-v2/anysee.c b/drivers/media/usb/dvb-usb-v2/anysee.c
>> index 8699846eb416..b2f5db961245 100644
>> --- a/drivers/media/usb/dvb-usb-v2/anysee.c
>> +++ b/drivers/media/usb/dvb-usb-v2/anysee.c
>> @@ -55,10 +55,8 @@ static int anysee_ctrl_msg(struct dvb_usb_device *d,
>>  
>>  	/* TODO FIXME: dvb_usb_generic_rw() fails rarely with error code -32
>>  	 * (EPIPE, Broken pipe). Function supports currently msleep() as a
>> -	 * parameter but I would not like to use it, since according to
>> -	 * Documentation/timers/timers-howto.rst it should not be used such
>> -	 * short, under < 20ms, sleeps. Repeating failed message would be
>> -	 * better choice as not to add unwanted delays...
>> +	 * parameter. Check msleep() for details. Repeating failed message would
>> +	 * be better choice as not to add unwanted delays...
>
> Does the comment still matches any up-to-date worry? It passes 2000 ms which is
> 2 seconds...

I had a closer look at it: dvb_usb_generic_rw() is no longer used. The
v2 interfaces are used anyway and this uses usleep_range() instead of
msleep().

I updated the patch and also talked to Sebastian. Will send an update
with v3 which removes and updates the comments.

> Thanks.
>
>>  	 * Fixing that correctly is one of those or both;
>>  	 * 1) use repeat if possible
>>  	 * 2) add suitable delay
>> 
>> -- 
>> 2.39.2
>>