[PATCH] lightweight robust futexes updates

- fix: initialize the robust list(s) to NULL in copy_process.

- doc update

- cleanup: rename _inuser to _inatomic

- __user cleanups and other small cleanups
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/robust-futex-ABI.txt

@@ -142,8 +142,6 @@ On insertion:
     of the 'lock word', to the linked list starting at 'head', and
  4) clear the 'list_op_pending' word.
 
-	XXX I am particularly unsure of the following -pj XXX
-
 On removal:
  1) set the 'list_op_pending' word to the address of the 'lock word'
     to be removed,

Documentation/robust-futexes.txt

@@ -213,6 +213,6 @@ robust-mutex testcases.
 All other architectures should build just fine too - but they wont have
 the new syscalls yet.
 
-Architectures need to implement the new futex_atomic_cmpxchg_inuser()
+Architectures need to implement the new futex_atomic_cmpxchg_inatomic()
 inline function before writing up the syscalls (that function returns
 -ENOSYS right now).

include/asm-frv/futex.h

@@ -10,7 +10,7 @@
 extern int futex_atomic_op_inuser(int encoded_op, int __user *uaddr);
 
 static inline int
-futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
 	return -ENOSYS;
 }

include/asm-generic/futex.h

@@ -50,7 +50,7 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
 }
 
 static inline int
-futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
 	return -ENOSYS;
 }

include/asm-i386/futex.h

@@ -105,7 +105,7 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
 }
 
 static inline int
-futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
 	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
 		return -EFAULT;

include/asm-mips/futex.h

@@ -100,7 +100,7 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
 }
 
 static inline int
-futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
 	return -ENOSYS;
 }

include/asm-powerpc/futex.h

@@ -82,7 +82,7 @@ static inline int futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
 }
 
 static inline int
-futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
 	return -ENOSYS;
 }

include/asm-x86_64/futex.h

@@ -95,7 +95,7 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
 }
 
 static inline int
-futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
+futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
 {
 	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
 		return -EFAULT;

include/linux/futex.h

@@ -100,7 +100,7 @@ long do_futex(unsigned long uaddr, int op, int val,
 		unsigned long timeout, unsigned long uaddr2, int val2,
 		int val3);
 
-extern int handle_futex_death(unsigned int *uaddr, struct task_struct *curr);
+extern int handle_futex_death(u32 __user *uaddr, struct task_struct *curr);
 
 #ifdef CONFIG_FUTEX
 extern void exit_robust_list(struct task_struct *curr);

kernel/fork.c

@@ -1061,7 +1061,10 @@ static task_t *copy_process(unsigned long clone_flags,
 	 * Clear TID on mm_release()?
 	 */
 	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
-
+	p->robust_list = NULL;
+#ifdef CONFIG_COMPAT
+	p->compat_robust_list = NULL;
+#endif
 	/*
 	 * sigaltstack should be cleared when sharing the same VM
 	 */

kernel/futex.c

@@ -913,15 +913,15 @@ sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr,
  * Process a futex-list entry, check whether it's owned by the
  * dying task, and do notification if so:
  */
-int handle_futex_death(unsigned int *uaddr, struct task_struct *curr)
+int handle_futex_death(u32 __user *uaddr, struct task_struct *curr)
 {
-	unsigned int futex_val;
+	u32 uval;
 
-repeat:
-	if (get_user(futex_val, uaddr))
+retry:
+	if (get_user(uval, uaddr))
 		return -1;
 
-	if ((futex_val & FUTEX_TID_MASK) == curr->pid) {
+	if ((uval & FUTEX_TID_MASK) == curr->pid) {
 		/*
 		 * Ok, this dying thread is truly holding a futex
 		 * of interest. Set the OWNER_DIED bit atomically
@@ -932,12 +932,11 @@ int handle_futex_death(unsigned int *uaddr, struct task_struct *curr)
 		 * thread-death.) The rest of the cleanup is done in
 		 * userspace.
 		 */
-		if (futex_atomic_cmpxchg_inuser(uaddr, futex_val,
-					 futex_val | FUTEX_OWNER_DIED) !=
-								   futex_val)
-			goto repeat;
+		if (futex_atomic_cmpxchg_inatomic(uaddr, uval,
+					 uval | FUTEX_OWNER_DIED) != uval)
+			goto retry;
 
-		if (futex_val & FUTEX_WAITERS)
+		if (uval & FUTEX_WAITERS)
 			futex_wake((unsigned long)uaddr, 1);
 	}
 	return 0;
@@ -985,7 +984,6 @@ void exit_robust_list(struct task_struct *curr)
 			if (handle_futex_death((void *)entry + futex_offset,
 						curr))
 				return;
-
 		/*
 		 * Fetch the next entry in the list:
 		 */

kernel/futex_compat.c

@@ -121,9 +121,9 @@ compat_sys_get_robust_list(int pid, compat_uptr_t *head_ptr,
 	return ret;
 }
 
-asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, int val,
+asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val,
 		struct compat_timespec __user *utime, u32 __user *uaddr2,
-		int val3)
+		u32 val3)
 {
 	struct timespec t;
 	unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
@@ -137,6 +137,5 @@ asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, int val,
 	if (op >= FUTEX_REQUEUE)
 		val2 = (int) (unsigned long) utime;
 
-	return do_futex((unsigned long)uaddr, op, val, timeout,
-			(unsigned long)uaddr2, val2, val3);
+	return do_futex(uaddr, op, val, timeout, uaddr2, val2, val3);
 }