[PATCH] getpriority: Only getpriority translation the priority values

[PATCH] getpriority: Only getpriority translation the priority values

[Theodore Dubois]

The translation is needed to avoid returning a negative number from a
successful syscall, and this requirement doesn't apply to setpriority.
See the implementation of getpriority in kernel/sys.c.

Signed-off-by: Theodore Dubois <tbodt@google.com>
---
 man2/getpriority.2 | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git man2/getpriority.2 man2/getpriority.2
index 3e1be3e6c..24c1b7f11 100644
--- man2/getpriority.2
+++ man2/getpriority.2
@@ -206,20 +206,11 @@ All BSD-like systems (SunOS 4.1.3, Ultrix 4.2,
 manner as Linux 2.6.12 and later.
 .\"
 .SS C library/kernel differences
-Within the kernel, nice values are actually represented
-using the range 40..1
-(since negative numbers are error codes) and these are the values
-employed by the
-.BR setpriority ()
-and
-.BR getpriority ()
-system calls.
-The glibc wrapper functions for these system calls handle the
-translations between the user-land and kernel representations
-of the nice value according to the formula
+The getpriority system call returns nice values translated to the range 40..1,
+since a negative return value would be interpreted as an error.
+The glibc wrapper function for getpriority translates the value back according to the formula
 .IR "unice\ =\ 20\ \-\ knice" .
-(Thus, the kernel's 40..1 range corresponds to the
-range \-20..19 as seen by user space.)
+(Thus, the 40..1 range returned by the kernel corresponds to the range \-20..19 as seen by user space.)
 .SH BUGS
 According to POSIX, the nice value is a per-process setting.
 However, under the current Linux/NPTL implementation of POSIX threads,
-- 
2.36.0.512.ge40c2bad7a-goog

Re: [PATCH] getpriority: Only getpriority translation the priority values

[Alejandro Colomar]

On 5/11/22 00:08, Theodore Dubois wrote:
> The translation is needed to avoid returning a negative number from a
> successful syscall, and this requirement doesn't apply to setpriority.
> See the implementation of getpriority in kernel/sys.c.

Confirmed.  See:

$ grepc -tf getpriority kernel/
./kernel/sys.c:274:
SYSCALL_DEFINE2(getpriority, int, which, int, who)
{
	...
			niceval = nice_to_rlimit(task_nice(p));
			if (niceval > retval)
				retval = niceval;
	...

	return retval;
}
$ grepc -tf setpriority kernel/
./kernel/sys.c:204:
SYSCALL_DEFINE3(setpriority, int, which, int, who, int, niceval)
{
	...
	if (niceval < MIN_NICE)
		niceval = MIN_NICE;
	if (niceval > MAX_NICE)
		niceval = MAX_NICE;

	...
}
$ grepc -tm M.._NICE
./include/linux/sched/prio.h:5:
#define MAX_NICE	19


./include/linux/sched/prio.h:6:
#define MIN_NICE	-20
$ grepc -tf nice_to_rlimit
./include/linux/sched/prio.h:32:
static inline long nice_to_rlimit(long nice)
{
	return (MAX_NICE - nice + 1);
}


-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH] getpriority: Only getpriority translation the priority values

[Alejandro Colomar]

Hi Theodore,

On 5/11/22 00:08, Theodore Dubois wrote:
> The translation is needed to avoid returning a negative number from a
> successful syscall, and this requirement doesn't apply to setpriority.
> See the implementation of getpriority in kernel/sys.c.
> 
> Signed-off-by: Theodore Dubois <tbodt@google.com>

Patch applied.

BTW, I had to manually edit the patch.
It's the second time I see this (I can't find the other one), your patch 
didn't apply for the following reason: the a/ and b/ prefixes in the 
file paths are missing.  Did you use git-format-patch(1) to produce the 
patch?  Can you reproduce this?

I CCd the git mailing list in case they know what's going on.

Thanks,

Alex

> ---
>   man2/getpriority.2 | 17 ++++-------------
>   1 file changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git man2/getpriority.2 man2/getpriority.2

Should have been:
diff --git a/man2/getpriority.2 b/man2/getpriority.2

> index 3e1be3e6c..24c1b7f11 100644
> --- man2/getpriority.2
> +++ man2/getpriority.2

Should have been:

--- a/man2/getpriority.2
+++ b/man2/getpriority.2


> @@ -206,20 +206,11 @@ All BSD-like systems (SunOS 4.1.3, Ultrix 4.2,
>   manner as Linux 2.6.12 and later.
>   .\"
>   .SS C library/kernel differences
> -Within the kernel, nice values are actually represented
> -using the range 40..1
> -(since negative numbers are error codes) and these are the values
> -employed by the
> -.BR setpriority ()
> -and
> -.BR getpriority ()
> -system calls.
> -The glibc wrapper functions for these system calls handle the
> -translations between the user-land and kernel representations
> -of the nice value according to the formula
> +The getpriority system call returns nice values translated to the range 40..1,
> +since a negative return value would be interpreted as an error.
> +The glibc wrapper function for getpriority translates the value back according to the formula
>   .IR "unice\ =\ 20\ \-\ knice" .
> -(Thus, the kernel's 40..1 range corresponds to the
> -range \-20..19 as seen by user space.)
> +(Thus, the 40..1 range returned by the kernel corresponds to the range \-20..19 as seen by user space.)
>   .SH BUGS
>   According to POSIX, the nice value is a per-process setting.
>   However, under the current Linux/NPTL implementation of POSIX threads,

-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH] getpriority: Only getpriority translation the priority values

[Alejandro Colomar]

[CC += nick]

On 5/14/22 16:37, Alejandro Colomar wrote:
> Hi Theodore,
> 
> On 5/11/22 00:08, Theodore Dubois wrote:
>> The translation is needed to avoid returning a negative number from a
>> successful syscall, and this requirement doesn't apply to setpriority.
>> See the implementation of getpriority in kernel/sys.c.
>>
>> Signed-off-by: Theodore Dubois <tbodt@google.com>
> 
> Patch applied.
> 
> BTW, I had to manually edit the patch.
> It's the second time I see this (I can't find the other one), your patch 

The other one:

<https://lore.kernel.org/linux-man/809c40c4-068b-8296-57d9-024e6623362d@gmail.com/T/#u>

nick, I finally found it again!

> didn't apply for the following reason: the a/ and b/ prefixes in the 
> file paths are missing.  Did you use git-format-patch(1) to produce the 
> patch?  Can you reproduce this?
> 
> I CCd the git mailing list in case they know what's going on.
> 
> Thanks,
> 
> Alex
> 
>> ---
>>   man2/getpriority.2 | 17 ++++-------------
>>   1 file changed, 4 insertions(+), 13 deletions(-)
>>
>> diff --git man2/getpriority.2 man2/getpriority.2
> 
> Should have been:
> diff --git a/man2/getpriority.2 b/man2/getpriority.2
> 
>> index 3e1be3e6c..24c1b7f11 100644
>> --- man2/getpriority.2
>> +++ man2/getpriority.2
> 
> Should have been:
> 
> --- a/man2/getpriority.2
> +++ b/man2/getpriority.2
> 
> 
>> @@ -206,20 +206,11 @@ All BSD-like systems (SunOS 4.1.3, Ultrix 4.2,
>>   manner as Linux 2.6.12 and later.
>>   .\"
>>   .SS C library/kernel differences
>> -Within the kernel, nice values are actually represented
>> -using the range 40..1
>> -(since negative numbers are error codes) and these are the values
>> -employed by the
>> -.BR setpriority ()
>> -and
>> -.BR getpriority ()
>> -system calls.
>> -The glibc wrapper functions for these system calls handle the
>> -translations between the user-land and kernel representations
>> -of the nice value according to the formula
>> +The getpriority system call returns nice values translated to the 
>> range 40..1,
>> +since a negative return value would be interpreted as an error.
>> +The glibc wrapper function for getpriority translates the value back 
>> according to the formula
>>   .IR "unice\ =\ 20\ \-\ knice" .
>> -(Thus, the kernel's 40..1 range corresponds to the
>> -range \-20..19 as seen by user space.)
>> +(Thus, the 40..1 range returned by the kernel corresponds to the 
>> range \-20..19 as seen by user space.)
>>   .SH BUGS
>>   According to POSIX, the nice value is a per-process setting.
>>   However, under the current Linux/NPTL implementation of POSIX threads,
> 

-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH] getpriority: Only getpriority translation the priority values

[Martin Ågren]

On Sat, 14 May 2022 at 17:11, Alejandro Colomar <alx.manpages@gmail.com> wrote:
>
> BTW, I had to manually edit the patch.
> It's the second time I see this (I can't find the other one), your patch
> didn't apply for the following reason: the a/ and b/ prefixes in the
> file paths are missing.  Did you use git-format-patch(1) to produce the
> patch?  Can you reproduce this?
>
> I CCd the git mailing list in case they know what's going on.

Sounds like `git format-patch --no-prefix` at play. Or more likely, that
the `diff.noprefix` config is on. I don't think it can be cancelled out
by a `--no-no-prefix`, unfortunately. If a script is involved in running
`git format-patch`, maybe it's not too tedious to make it do

  git -c diff.noprefix=no format-patch ...

to cancel the config. (If that config really does want to be on, that
is.)

That said, something like

  git am -p0 ...

should help on the receiving side, by way of skipping fewer path
components when applying the patch.

Martin

Re: [PATCH] getpriority: Only getpriority translation the priority values

[Alejandro Colomar]

Hi Martin,

On 5/14/22 20:43, Martin Ågren wrote:
> That said, something like
> 
>    git am -p0 ...
> 
> should help on the receiving side, by way of skipping fewer path
> components when applying the patch.

That works for me.
Thanks!

Alex

-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH] getpriority: Only getpriority translation the priority values

[Theodore Dubois]

Yep, I have diff.noprefix on.

~Theodore

On Sat, May 14, 2022 at 11:43 AM Martin Ågren <martin.agren@gmail.com> wrote:
>
> On Sat, 14 May 2022 at 17:11, Alejandro Colomar <alx.manpages@gmail.com> wrote:
> >
> > BTW, I had to manually edit the patch.
> > It's the second time I see this (I can't find the other one), your patch
> > didn't apply for the following reason: the a/ and b/ prefixes in the
> > file paths are missing.  Did you use git-format-patch(1) to produce the
> > patch?  Can you reproduce this?
> >
> > I CCd the git mailing list in case they know what's going on.
>
> Sounds like `git format-patch --no-prefix` at play. Or more likely, that
> the `diff.noprefix` config is on. I don't think it can be cancelled out
> by a `--no-no-prefix`, unfortunately. If a script is involved in running
> `git format-patch`, maybe it's not too tedious to make it do
>
>   git -c diff.noprefix=no format-patch ...
>
> to cancel the config. (If that config really does want to be on, that
> is.)
>
> That said, something like
>
>   git am -p0 ...
>
> should help on the receiving side, by way of skipping fewer path
> components when applying the patch.
>
> Martin

Perhaps we want {diff,log,format}.noprefix and friends?

[Junio C Hamano]

>>   git -c diff.noprefix=no format-patch ...
>>
>> to cancel the config. (If that config really does want to be on, that
>> is.)
>>
>> That said, something like
>>
>>   git am -p0 ...
>>
>> should help on the receiving side, by way of skipping fewer path
>> components when applying the patch.

While it is very reasonable for end-users to make the output of
their local "git diff" output to their taste by setting the
diff.noprefix and other configuration options in the diff.*
namespace, it is wrong to inflict such a personal preference on
other project participants by sending such a no-prefix patch via
"git format-patch", when the convention at the receiving project is
to use "git am -p1" to accept them.

We would need to tweak the configuration system so that we can more
easily introduce "format.noprefix" that overrides "diff.noprefix"
only when the command being run is "git format-patch", perhaps?  

As things stand, we could teach builtin/log.c::git_format_config()
about "format.noprefix" and make "git format-patch" pay attention to
that in addition to "diff.noprefix" fairly easily, but such an
approach poorly scales.  When a new configuration gets introduced in
diff.c::git_diff_ui_config(), builtin/log.c::git_format_config()
would also need to be updated.

I initially started writing this with "left over bits" mark, but it
seems it is a bit larger in scope than that.

I also noticed that some format.* configuration variables are parsed
in git_log_config(), not git_format_config(), so "git log" would end
up honoring format.pretty and format.subjectprefix, etc., which look
wrong but probably is way too late to "fix".