nptl: Make pthread_attr_t dynamically extensible

This introduces the function __pthread_attr_extension to allocate the
extension space, which is freed by pthread_attr_destroy.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

2 files changed, 19 insertions, 6 deletions

diff --git a/sysdeps/nptl/internaltypes.h b/sysdeps/nptl/internaltypes.h
index 6d06a76baf..ca57c315d4 100644
--- a/sysdeps/nptl/internaltypes.h
+++ b/sysdeps/nptl/internaltypes.h
@@ -36,9 +36,10 @@ struct pthread_attr
   /* Stack handling.  */
   void *stackaddr;
   size_t stacksize;
-  /* Affinity map.  */
-  cpu_set_t *cpuset;
-  size_t cpusetsize;
+
+  /* Allocated via a call to __pthread_attr_extension once needed.  */
+  struct pthread_attr_extension *extension;
+  void *unused;
 };
 
 #define ATTR_FLAG_DETACHSTATE		0x0001
@@ -57,6 +58,15 @@ union pthread_attr_transparent
   struct pthread_attr internal;
 };
 
+/* Extension space for pthread attributes.  Referenced by the
+   extension member of struct pthread_attr.  */
+struct pthread_attr_extension
+{
+  /* Affinity map.  */
+  cpu_set_t *cpuset;
+  size_t cpusetsize;
+};
+
 /* Mutex attribute data structure.  */
 struct pthread_mutexattr
 {
diff --git a/sysdeps/unix/sysv/linux/createthread.c b/sysdeps/unix/sysv/linux/createthread.c
index 21f9d24f2d..6588893ba5 100644
--- a/sysdeps/unix/sysv/linux/createthread.c
+++ b/sysdeps/unix/sysv/linux/createthread.c
@@ -52,8 +52,10 @@ create_thread (struct pthread *pd, const struct pthread_attr *attr,
   /* Determine whether the newly created threads has to be started
      stopped since we have to set the scheduling parameters or set the
      affinity.  */
+  bool need_setaffinity = (attr != NULL && attr->extension != NULL
+			   && attr->extension->cpuset != 0);
   if (attr != NULL
-      && (__glibc_unlikely (attr->cpuset != NULL)
+      && (__glibc_unlikely (need_setaffinity)
 	  || __glibc_unlikely ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)))
     *stopped_start = true;
 
@@ -113,12 +115,13 @@ create_thread (struct pthread *pd, const struct pthread_attr *attr,
       int res;
 
       /* Set the affinity mask if necessary.  */
-      if (attr->cpuset != NULL)
+      if (need_setaffinity)
 	{
 	  assert (*stopped_start);
 
 	  res = INTERNAL_SYSCALL_CALL (sched_setaffinity, pd->tid,
-				       attr->cpusetsize, attr->cpuset);
+				       attr->extension->cpusetsize,
+				       attr->extension->cpuset);
 
 	  if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res)))
 	  err_out: