[LTP] [PATCH] lapi/sched: Fix sched_getattr/setattr fallback definitions

[Wake Liu]

Commit c48700d8cdbe ("sched_attr: Do not define for glibc >= 2.41")
guarded the definitions of struct sched_attr, sched_setattr(), and
sched_getattr() under "#ifndef SCHED_ATTR_SIZE_VER0" to avoid conflicts
when glibc >= 2.41 provides these definitions.

However, SCHED_ATTR_SIZE_VER0 is a standard Linux kernel UAPI macro
defined in <linux/sched/types.h>. When headers include the kernel types
(such as on Android Bionic, musl, or older glibc with kernel headers),
SCHED_ATTR_SIZE_VER0 is defined even though libc does not provide the
sched_setattr() or sched_getattr() functions. This causes the fallback
syscall wrappers to be omitted, leading to unresolved symbol errors.

Add autotools checks for sched_getattr, sched_setattr, and
struct sched_attr. Guard the fallback functions with
HAVE_SCHED_GETATTR and HAVE_SCHED_SETATTR, and remove const from
sched_setattr's attr parameter to match the kernel and libc signatures.

Fixes: c48700d8cdbe ("sched_attr: Do not define for glibc >= 2.41")
Signed-off-by: Wake Liu <wakel@google.com>
---
 configure.ac         |  3 +++
 include/lapi/sched.h | 16 ++++++++++------
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/configure.ac b/configure.ac
index 19fc5e1b8..8aa3ff539 100644
--- a/configure.ac
+++ b/configure.ac
@@ -155,7 +155,9 @@ AC_CHECK_FUNCS_ONCE([ \
     rand_r \
     recvmmsg \
     renameat2 \
+    sched_getattr \
     sched_getcpu \
+    sched_setattr \
     sendmmsg \
     sethostid \
     setns \
@@ -199,6 +201,7 @@ AC_CHECK_DECLS([TCA_PEDIT_PARMS_EX, TCA_PEDIT_KEYS_EX, TCA_PEDIT_KEY_EX,
 AC_CHECK_TYPES([struct acct_v3],,,[#include <sys/acct.h>])
 AC_CHECK_TYPES([struct af_alg_iv, struct sockaddr_alg],,,[# include <linux/if_alg.h>])
 AC_CHECK_TYPES([struct clone_args],,,[#include <sched.h>])
+AC_CHECK_TYPES([struct sched_attr],,,[#include <sched.h>])
 AC_CHECK_TYPES([struct fanotify_event_info_fid, struct fanotify_event_info_error,
 		struct fanotify_event_info_header, struct fanotify_event_info_pidfd,
 		struct fanotify_event_info_range],,,[#include <sys/fanotify.h>])
diff --git a/include/lapi/sched.h b/include/lapi/sched.h
index 05b322c1c..d835537e7 100644
--- a/include/lapi/sched.h
+++ b/include/lapi/sched.h
@@ -14,8 +14,8 @@
 #include "config.h"
 #include "lapi/syscalls.h"
 
-/* sched_attr is not defined in glibc < 2.41 */
 #ifndef SCHED_ATTR_SIZE_VER0
+# ifndef HAVE_STRUCT_SCHED_ATTR
 struct sched_attr {
 	uint32_t size;
 
@@ -33,20 +33,24 @@ struct sched_attr {
 	uint64_t sched_deadline;
 	uint64_t sched_period;
 };
+# endif
+# define SCHED_ATTR_SIZE_VER0 48	/* sizeof first published struct */
+#endif
 
-static inline int sched_setattr(pid_t pid, const struct sched_attr *attr,
-                                unsigned int flags)
+#ifndef HAVE_SCHED_SETATTR
+static inline int sched_setattr(pid_t pid, struct sched_attr *attr,
+				unsigned int flags)
 {
 	return syscall(__NR_sched_setattr, pid, attr, flags);
 }
+#endif
 
+#ifndef HAVE_SCHED_GETATTR
 static inline int sched_getattr(pid_t pid, struct sched_attr *attr,
-                                unsigned int size, unsigned int flags)
+				unsigned int size, unsigned int flags)
 {
 	return syscall(__NR_sched_getattr, pid, attr, size, flags);
 }
-
-# define SCHED_ATTR_SIZE_VER0 48	/* sizeof first published struct */
 #endif
 
 struct clone_args_minimal {
-- 
2.55.0.966.g6673acef38-goog