[PATCH] Fix clock_nanosleep() signal restart issues

The problem with clock_nanosleep() restarting was that the address of
the users return timespec was being saved at the wrong place.  In needs
to be saved in the sys call interface code rather than the
do_clock_nanosleep().  My original tests were a bit weak as they only
did one signal rather than two or more which were required to break it. 

The attached patch fixes the problem.

I also added a few comments about how restart works, and added my name
to the MAINTAINERS list.

MAINTAINERS

@@ -1568,6 +1568,12 @@ M:	tsbogend@alpha.franken.de
 L:	linux-net@vger.kernel.org
 S:	Maintained
 
+POSIX CLOCKS and TIMERS
+P:	George Anzinger
+M:	george@mvista.com
+L:	linux-net@vger.kernel.org
+S:	Supported
+
 PNP SUPPORT
 P:	Adam Belay
 M:	ambx1@neo.rr.com

kernel/posix-timers.c

@@ -1110,6 +1110,8 @@ sys_clock_nanosleep(clockid_t which_clock, int flags,
 		    struct timespec __user *rmtp)
 {
 	struct timespec t;
+	struct restart_block *restart_block =
+	    &(current_thread_info()->restart_block);
 	int ret;
 
 	if ((unsigned) which_clock >= MAX_CLOCKS ||
@@ -1123,6 +1125,10 @@ sys_clock_nanosleep(clockid_t which_clock, int flags,
 		return -EINVAL;
 
 	ret = do_clock_nanosleep(which_clock, flags, &t);
+	/*
+	 * Do this here as do_clock_nanosleep does not have the real address
+	 */
+	restart_block->arg1 = (unsigned long)rmtp;
 
 	if ((ret == -ERESTART_RESTARTBLOCK) && rmtp &&
 					copy_to_user(rmtp, &t, sizeof (t)))
@@ -1152,7 +1158,7 @@ do_clock_nanosleep(clockid_t which_clock, int flags, struct timespec *tsave)
 	if (restart_block->fn == clock_nanosleep_restart) {
 		/*
 		 * Interrupted by a non-delivered signal, pick up remaining
-		 * time and continue.
+		 * time and continue.  Remaining time is in arg2 & 3.
 		 */
 		restart_block->fn = do_no_restart_syscall;
 
@@ -1209,9 +1215,20 @@ do_clock_nanosleep(clockid_t which_clock, int flags, struct timespec *tsave)
 		tsave->tv_sec = div_long_long_rem(left, 
 						  NSEC_PER_SEC, 
 						  &tsave->tv_nsec);
+		/*
+		 * Restart works by saving the time remaing in 
+		 * arg2 & 3 (it is 64-bits of jiffies).  The other
+		 * info we need is the clock_id (saved in arg0). 
+		 * The sys_call interface needs the users 
+		 * timespec return address which _it_ saves in arg1.
+		 * Since we have cast the nanosleep call to a clock_nanosleep
+		 * both can be restarted with the same code.
+		 */
 		restart_block->fn = clock_nanosleep_restart;
 		restart_block->arg0 = which_clock;
-		restart_block->arg1 = (unsigned long)tsave;
+		/*
+		 * Caller sets arg1
+		 */
 		restart_block->arg2 = rq_time & 0xffffffffLL;
 		restart_block->arg3 = rq_time >> 32;
 
@@ -1221,7 +1238,7 @@ do_clock_nanosleep(clockid_t which_clock, int flags, struct timespec *tsave)
 	return 0;
 }
 /*
- * This will restart clock_nanosleep. Incorrectly, btw.
+ * This will restart clock_nanosleep.
  */
 long
 clock_nanosleep_restart(struct restart_block *restart_block)