2006-12-21  Ulrich Drepper  <drepper@redhat.com>

	* include/atomic.h (atomic_forced_read): New macro.
nptl/
2006-12-21  Jakub Jelinek  <jakub@redhat.com>

	* sysdeps/unix/sysv/linux/pthread_kill.c (pthread_kill): Make sure
	tid isn't reread from pd->tid in between ESRCH test and the syscall.

--- libc/include/atomic.h	18 Oct 2006 19:02:53 -0000	1.20
+++ libc/include/atomic.h	21 Dec 2006 21:44:00 -0000	1.21
@@ -497,6 +497,12 @@
 #endif
 
 
+#ifndef atomic_forced_read
+# define atomic_forced_read(x) \
+  ({ __typeof (x) __x; __asm ("" : "=r" (__x) : "0" (x)); __x; })
+#endif
+
+
 #ifndef atomic_delay
 # define atomic_delay() do { /* nothing */ } while (0)
 #endif
--- libc/nptl/sysdeps/unix/sysv/linux/pthread_kill.c	28 Sep 2004 22:22:37 -0000	1.12
+++ libc/nptl/sysdeps/unix/sysv/linux/pthread_kill.c	22 Dec 2006 00:35:21 -0000	1.14
@@ -33,7 +33,15 @@ __pthread_kill (threadid, signo)
   struct pthread *pd = (struct pthread *) threadid;
 
   /* Make sure the descriptor is valid.  */
-  if (INVALID_TD_P (pd))
+  if (DEBUGGING_P && INVALID_TD_P (pd))
+    /* Not a valid thread handle.  */
+    return ESRCH;
+
+  /* Force load of pd->tid into local variable or register.  Otherwise
+     if a thread exits between ESRCH test and tgkill, we might return
+     EINVAL, because pd->tid would be cleared by the kernel.  */
+  pid_t tid = atomic_forced_read (pd->tid);
+  if (__builtin_expect (tid <= 0, 0))
     /* Not a valid thread handle.  */
     return ESRCH;
 
@@ -53,15 +61,15 @@ __pthread_kill (threadid, signo)
   int val;
 #if __ASSUME_TGKILL
   val = INTERNAL_SYSCALL (tgkill, err, 3, THREAD_GETMEM (THREAD_SELF, pid),
-			  pd->tid, signo);
+			  tid, signo);
 #else
 # ifdef __NR_tgkill
   val = INTERNAL_SYSCALL (tgkill, err, 3, THREAD_GETMEM (THREAD_SELF, pid),
-			  pd->tid, signo);
+			  tid, signo);
   if (INTERNAL_SYSCALL_ERROR_P (val, err)
       && INTERNAL_SYSCALL_ERRNO (val, err) == ENOSYS)
 # endif
-    val = INTERNAL_SYSCALL (tkill, err, 2, pd->tid, signo);
+    val = INTERNAL_SYSCALL (tkill, err, 2, tid, signo);
 #endif
 
   return (INTERNAL_SYSCALL_ERROR_P (val, err)