[PATCH] sched_attr: Do not define for glibc >= 2.41

[PATCH] sched_attr: Do not define for glibc >= 2.41

[Khem Raj]

glibc 2.41+ has added [1] definitions for sched_setattr and sched_getattr functions
and struct sched_attr. Therefore, it needs to be checked for here as well before
defining sched_attr

Define sched_attr conditionally on SCHED_ATTR_SIZE_VER0

Fixes builds with glibc/trunk

[1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=21571ca0d70302909cf72707b2a7736cf12190a0;hp=298bc488fdc047da37482f4003023cb9adef78f8

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: rt-users <linux-rt-users@vger.kernel.org>
---
 src/include/rt-sched.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/include/rt-sched.h b/src/include/rt-sched.h
index 80171c7..9cf0e3a 100644
--- a/src/include/rt-sched.h
+++ b/src/include/rt-sched.h
@@ -42,6 +42,8 @@
 #define __NR_sched_getattr		275
 #endif
 
+/* sched_attr is not defined in glibc < 2.41 */
+#ifndef SCHED_ATTR_SIZE_VER0
 struct sched_attr {
 	uint32_t size;
 	uint32_t sched_policy;
@@ -68,4 +70,6 @@ int sched_getattr(pid_t pid,
 		  unsigned int size,
 		  unsigned int flags);
 
+#endif /* SCHED_ATTR_SIZE_VER0 */
+
 #endif /* __RT_SCHED_H__ */

[PATCH] sched_attr: Do not define for glibc >= 2.41

[Khem Raj]

glibc 2.41+ has added [1] definitions for sched_setattr and sched_getattr functions
and struct sched_attr. Therefore, it needs to be checked for here as well before
defining sched_attr

Define sched_attr conditionally on SCHED_ATTR_SIZE_VER0

Fixes builds with glibc/trunk

[1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=21571ca0d70302909cf72707b2a7736cf12190a0;hp=298bc488fdc047da37482f4003023cb9adef78f8

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: rt-users <linux-rt-users@vger.kernel.org>
---
 src/include/rt-sched.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/include/rt-sched.h b/src/include/rt-sched.h
index 80171c7..9cf0e3a 100644
--- a/src/include/rt-sched.h
+++ b/src/include/rt-sched.h
@@ -42,6 +42,8 @@
 #define __NR_sched_getattr		275
 #endif
 
+/* sched_attr is not defined in glibc < 2.41 */
+#ifndef SCHED_ATTR_SIZE_VER0
 struct sched_attr {
 	uint32_t size;
 	uint32_t sched_policy;
@@ -68,4 +70,6 @@ int sched_getattr(pid_t pid,
 		  unsigned int size,
 		  unsigned int flags);
 
+#endif /* SCHED_ATTR_SIZE_VER0 */
+
 #endif /* __RT_SCHED_H__ */

Re: [PATCH] sched_attr: Do not define for glibc >= 2.41

[John Kacur]

On Tue, 28 Jan 2025, Khem Raj wrote:

> glibc 2.41+ has added [1] definitions for sched_setattr and sched_getattr functions
> and struct sched_attr. Therefore, it needs to be checked for here as well before
> defining sched_attr
> 
> Define sched_attr conditionally on SCHED_ATTR_SIZE_VER0
> 
> Fixes builds with glibc/trunk
> 
> [1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=21571ca0d70302909cf72707b2a7736cf12190a0;hp=298bc488fdc047da37482f4003023cb9adef78f8
> 
> Signed-off-by: Khem Raj <raj.khem@gmail.com>
> Cc: Clark Williams <williams@redhat.com>
> Cc: John Kacur <jkacur@redhat.com>
> Cc: rt-users <linux-rt-users@vger.kernel.org>
> ---
>  src/include/rt-sched.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/src/include/rt-sched.h b/src/include/rt-sched.h
> index 80171c7..9cf0e3a 100644
> --- a/src/include/rt-sched.h
> +++ b/src/include/rt-sched.h
> @@ -42,6 +42,8 @@
>  #define __NR_sched_getattr		275
>  #endif
>  
> +/* sched_attr is not defined in glibc < 2.41 */
> +#ifndef SCHED_ATTR_SIZE_VER0
>  struct sched_attr {
>  	uint32_t size;
>  	uint32_t sched_policy;
> @@ -68,4 +70,6 @@ int sched_getattr(pid_t pid,
>  		  unsigned int size,
>  		  unsigned int flags);
>  
> +#endif /* SCHED_ATTR_SIZE_VER0 */
> +
>  #endif /* __RT_SCHED_H__ */
> 
> 

Does the following fix your problem?

From 280e198c39d1b17d0491d7c4e7afda97ae6c8e6f Mon Sep 17 00:00:00 2001
From: Yaakov Selkowitz <yselkowi@redhat.com>
Date: Wed, 29 Jan 2025 16:46:11 -0500
Subject: [PATCH] Fix rt-tests build with glibc-2.41

The sched_*attr APIs were added to glibc
https://sourceware.org/git/?p=glibc.git;a=commit;h=21571ca0d70302909cf72707b2a7736cf12190a0

This fixes the build conflict in rt-tests with glibc-2.4

Signed-off-by: Yaakov Selkowitz <yselkowi@redhat.com>
Signed-off-by: John Kacur <jkacur@redhat.com>
---
 src/include/rt-sched.h | 2 ++
 src/lib/rt-sched.c     | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/src/include/rt-sched.h b/src/include/rt-sched.h
index 80171c76e0ee..dfd7f45f51cc 100644
--- a/src/include/rt-sched.h
+++ b/src/include/rt-sched.h
@@ -42,6 +42,7 @@
 #define __NR_sched_getattr		275
 #endif
 
+#if ! __GLIBC_PREREQ(2, 41)
 struct sched_attr {
 	uint32_t size;
 	uint32_t sched_policy;
@@ -67,5 +68,6 @@ int sched_getattr(pid_t pid,
 		  struct sched_attr *attr,
 		  unsigned int size,
 		  unsigned int flags);
+#endif
 
 #endif /* __RT_SCHED_H__ */
diff --git a/src/lib/rt-sched.c b/src/lib/rt-sched.c
index 8023bc70c473..2500abde26e4 100644
--- a/src/lib/rt-sched.c
+++ b/src/lib/rt-sched.c
@@ -14,6 +14,7 @@
 
 #include "rt-sched.h"
 
+#if ! __GLIBC_PREREQ(2, 41)
 int sched_setattr(pid_t pid,
 		  const struct sched_attr *attr,
 		  unsigned int flags)
@@ -28,3 +29,4 @@ int sched_getattr(pid_t pid,
 {
 	return syscall(__NR_sched_getattr, pid, attr, size, flags);
 }
+#endif
-- 
2.47.1

Re: [PATCH] sched_attr: Do not define for glibc >= 2.41

[Crystal Wood]

On Wed, 2025-01-29 at 16:54 -0500, John Kacur wrote:
> 
> On Tue, 28 Jan 2025, Khem Raj wrote:
> 
> > glibc 2.41+ has added [1] definitions for sched_setattr and sched_getattr functions
> > and struct sched_attr. Therefore, it needs to be checked for here as well before
> > defining sched_attr
> > 
> > Define sched_attr conditionally on SCHED_ATTR_SIZE_VER0
> > 
> > Fixes builds with glibc/trunk
> > 
> > [1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=21571ca0d70302909cf72707b2a7736cf12190a0;hp=298bc488fdc047da37482f4003023cb9adef78f8
> > 
> > Signed-off-by: Khem Raj <raj.khem@gmail.com>
> > Cc: Clark Williams <williams@redhat.com>
> > Cc: John Kacur <jkacur@redhat.com>
> > Cc: rt-users <linux-rt-users@vger.kernel.org>
> > ---
> >  src/include/rt-sched.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/src/include/rt-sched.h b/src/include/rt-sched.h
> > index 80171c7..9cf0e3a 100644
> > --- a/src/include/rt-sched.h
> > +++ b/src/include/rt-sched.h
> > @@ -42,6 +42,8 @@
> >  #define __NR_sched_getattr		275
> >  #endif
> >  
> > +/* sched_attr is not defined in glibc < 2.41 */
> > +#ifndef SCHED_ATTR_SIZE_VER0
> >  struct sched_attr {
> >  	uint32_t size;
> >  	uint32_t sched_policy;
> > @@ -68,4 +70,6 @@ int sched_getattr(pid_t pid,
> >  		  unsigned int size,
> >  		  unsigned int flags);
> >  
> > +#endif /* SCHED_ATTR_SIZE_VER0 */
> > +
> >  #endif /* __RT_SCHED_H__ */
> > 
> > 
> 
> Does the following fix your problem?
[snip]

> +#if ! __GLIBC_PREREQ(2, 41)

I'm not familiar with the norms surrounding use of this macro, but it's
generally better to test features than versions... what if this feature
gets backported into some distro's earlier-version-numbered glibc?

FWIW, it looks like QEMU went with the feature test approach:
https://patchwork.ozlabs.org/project/qemu-devel/patch/20241011054806.1014276-1-raj.khem@gmail.com/
https://patchwork.ozlabs.org/project/qemu-devel/patch/20241011193140.1047648-1-raj.khem@gmail.com/

Also, was that patch posted anywhere?  Just wondering if I've still got
problems with email filtering.

-Crystal

Re: [PATCH] sched_attr: Do not define for glibc >= 2.41

[John Kacur]

On Wed, 29 Jan 2025, Crystal Wood wrote:

> On Wed, 2025-01-29 at 16:54 -0500, John Kacur wrote:
> > 
> > On Tue, 28 Jan 2025, Khem Raj wrote:
> > 
> > > glibc 2.41+ has added [1] definitions for sched_setattr and sched_getattr functions
> > > and struct sched_attr. Therefore, it needs to be checked for here as well before
> > > defining sched_attr
> > > 
> > > Define sched_attr conditionally on SCHED_ATTR_SIZE_VER0
> > > 
> > > Fixes builds with glibc/trunk
> > > 
> > > [1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=21571ca0d70302909cf72707b2a7736cf12190a0;hp=298bc488fdc047da37482f4003023cb9adef78f8
> > > 
> > > Signed-off-by: Khem Raj <raj.khem@gmail.com>
> > > Cc: Clark Williams <williams@redhat.com>
> > > Cc: John Kacur <jkacur@redhat.com>
> > > Cc: rt-users <linux-rt-users@vger.kernel.org>
> > > ---
> > >  src/include/rt-sched.h | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/src/include/rt-sched.h b/src/include/rt-sched.h
> > > index 80171c7..9cf0e3a 100644
> > > --- a/src/include/rt-sched.h
> > > +++ b/src/include/rt-sched.h
> > > @@ -42,6 +42,8 @@
> > >  #define __NR_sched_getattr		275
> > >  #endif
> > >  
> > > +/* sched_attr is not defined in glibc < 2.41 */
> > > +#ifndef SCHED_ATTR_SIZE_VER0
> > >  struct sched_attr {
> > >  	uint32_t size;
> > >  	uint32_t sched_policy;
> > > @@ -68,4 +70,6 @@ int sched_getattr(pid_t pid,
> > >  		  unsigned int size,
> > >  		  unsigned int flags);
> > >  
> > > +#endif /* SCHED_ATTR_SIZE_VER0 */
> > > +
> > >  #endif /* __RT_SCHED_H__ */
> > > 
> > > 
> > 
> > Does the following fix your problem?
> [snip]
> 
> > +#if ! __GLIBC_PREREQ(2, 41)
> 
> I'm not familiar with the norms surrounding use of this macro, but it's
> generally better to test features than versions... what if this feature
> gets backported into some distro's earlier-version-numbered glibc?

The macro is part of the glibc code in features.h
You make a good point about testing the features, but you could also argue 
that there is no guarantee that the implementation will always have 
SCHED_ATTR_SIZE_VER0 and that it could break in the future.

> 
> FWIW, it looks like QEMU went with the feature test approach:
> https://patchwork.ozlabs.org/project/qemu-devel/patch/20241011054806.1014276-1-raj.khem@gmail.com/
> https://patchwork.ozlabs.org/project/qemu-devel/patch/20241011193140.1047648-1-raj.khem@gmail.com/
> 
Well, that's by the same author who sent this patch.


> Also, was that patch posted anywhere?  Just wondering if I've still got
> problems with email filtering.

No, a version of this was sent to me in fedora channels to fix a break in 
rawhide.

The version is more complete than the other patch because it also fixes 
src/lib/rt-sched.c

If this works for folks, lets just use it and move on, it's not worth 
endlessly hashing out.

John Kacur

> 
> -Crystal
> 
> 
>