Re: lib/53495: sched_get_priority_max/sched_get_priority_min not returning useful values

[Kamil Rytarowski <n54%gmx.com@localhost>]

The following reply was made to PR lib/53495; it has been noted by GNATS.

From: Kamil Rytarowski <n54%gmx.com@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: lib/53495: sched_get_priority_max/sched_get_priority_min not
 returning useful values
Date: Fri, 3 Aug 2018 03:51:30 +0200

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 From: Kamil Rytarowski <n54%gmx.com@localhost>
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 Subject: Re: lib/53495: sched_get_priority_max/sched_get_priority_min not
  returning useful values
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  <20180802213550.3008D2AC0E7%yt.nih.at@localhost>
  <20180802214000.8D1F77A14F%mollari.NetBSD.org@localhost>
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 This is not a bug. It works as intended.
 
 NetBSD behavior is compliant with POSIX and 3rd party program has to be
 fixed and handle the -1 case on its own, if there is need to distinguish
 error and unsupported, there is an option to reset errno and check it
 after the call.
 
 On 02.08.2018 23:40, Thomas Klausner wrote:
 >> Number:         53495
 >> Category:       lib
 >> Synopsis:       sched_get_priority_max/sched_get_priority_min not retu=
 rning useful values
 >> Confidential:   no
 >> Severity:       serious
 >> Priority:       low
 >> Responsible:    lib-bug-people
 >> State:          open
 >> Class:          sw-bug
 >> Submitter-Id:   net
 >> Arrival-Date:   Thu Aug 02 21:40:00 +0000 2018
 >> Originator:     Thomas Klausner
 >> Release:        NetBSD 8.99.22
 >> Organization:
 > Curiosity is the very basis of education and if you tell me that=20
 > curiosity killed the cat, I say only that the cat died nobly.
 > - Arnold Edinborough
 >> Environment:
 > =09
 > =09
 > Architecture: x86_64
 > Machine: amd64
 >> Description:
 > The man page describes the functions as follows:
 >=20
 >      sched_get_priority_max(policy)
 >               Returns the maximal priority which may be used for the
 >               scheduling policy specified by policy.
 >=20
 >      sched_get_priority_min(policy)
 >               Returns the minimal priority which may be used for the
 >               scheduling policy specified by policy.
 >=20
 > and later:
 >=20
 >      sched_get_priority_max() and sched_get_priority_min() return the
 >      maximal/minimal priority value on success.  Otherwise, -1 is retur=
 ned and
 >      errno is set to indicate the error.
 >=20
 > So programs check for "-1" to detect errors.
 >=20
 > However, in NetBSD, -1 is also returned in other cases, see
 > /usr/src/lib/libc/sys/sched.c:
 >=20
 > int
 > sched_get_priority_min(int policy)
 > {
 >=20
 >         switch (policy) {
 >         case SCHED_OTHER:
 >                 return PRI_NONE;
 >         case SCHED_RR:
 >         case SCHED_FIFO:
 >                 return (int)sysconf(_SC_SCHED_PRI_MIN);
 >         default:
 >                 errno =3D EINVAL;
 >                 return -1;
 >         }
 > }
 >=20
 >=20
 > and
 >=20
 > /usr/include/sys/param.h:#define        PRI_NONE                (-1)
 >=20
 > I'm not sure what the correct fix is. I suggest returning 0 instead of =
 -1;
 > I don't know what the definition of PRI_NONE is supposed to be and if t=
 hat
 > should be changed, or if the return value should just be zero for both
 > functions and not use PRI_NONE.
 >=20
 >> How-To-Repeat:
 >=20
 > #include <sched.h>
 > int main() {
 > printf("%d-%d\n", sched_get_priority_max(0), sched_get_priority_min(0))=
 ;
 > }
 >=20
 > gives:
 >=20
 > -1--1
 >=20
 >=20
 > Worse, wxGTK30 pops up unnecessary error messages at runtime.
 >=20
 >> Fix:
 > Return 0, and/or redefine PRI_NONE.
 >=20
 >> Unformatted:
 >  =09
 >  =09
 >=20
 
 
 
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