Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fix from Ingo Molnar:
 "This tree fixes a boot crash in CONFIG_DEBUG_MUTEXES=y kernels, on
  kernels built with GCC 3.x (there are still such distros)"

Side note: it's not just a fix for old gcc versions, it's also removing
an incredibly broken/subtle check that LLVM had issues with, and that
made no sense.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  mutex: Avoid gcc version dependent __builtin_constant_p() usage

Author: torvalds

kernel/mutex.c

@@ -410,7 +410,7 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock,
 static __always_inline int __sched
 __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		    struct lockdep_map *nest_lock, unsigned long ip,
-		    struct ww_acquire_ctx *ww_ctx)
+		    struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
 {
 	struct task_struct *task = current;
 	struct mutex_waiter waiter;
@@ -450,7 +450,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		struct task_struct *owner;
 		struct mspin_node  node;
 
-		if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
+		if (use_ww_ctx && ww_ctx->acquired > 0) {
 			struct ww_mutex *ww;
 
 			ww = container_of(lock, struct ww_mutex, base);
@@ -480,7 +480,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		if ((atomic_read(&lock->count) == 1) &&
 		    (atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
 			lock_acquired(&lock->dep_map, ip);
-			if (!__builtin_constant_p(ww_ctx == NULL)) {
+			if (use_ww_ctx) {
 				struct ww_mutex *ww;
 				ww = container_of(lock, struct ww_mutex, base);
 
@@ -551,7 +551,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 			goto err;
 		}
 
-		if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
+		if (use_ww_ctx && ww_ctx->acquired > 0) {
 			ret = __mutex_lock_check_stamp(lock, ww_ctx);
 			if (ret)
 				goto err;
@@ -575,7 +575,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 	lock_acquired(&lock->dep_map, ip);
 	mutex_set_owner(lock);
 
-	if (!__builtin_constant_p(ww_ctx == NULL)) {
+	if (use_ww_ctx) {
 		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
 		struct mutex_waiter *cur;
 
@@ -615,7 +615,7 @@ mutex_lock_nested(struct mutex *lock, unsigned int subclass)
 {
 	might_sleep();
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
-			    subclass, NULL, _RET_IP_, NULL);
+			    subclass, NULL, _RET_IP_, NULL, 0);
 }
 
 EXPORT_SYMBOL_GPL(mutex_lock_nested);
@@ -625,7 +625,7 @@ _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
 {
 	might_sleep();
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
-			    0, nest, _RET_IP_, NULL);
+			    0, nest, _RET_IP_, NULL, 0);
 }
 
 EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
@@ -635,7 +635,7 @@ mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
 {
 	might_sleep();
 	return __mutex_lock_common(lock, TASK_KILLABLE,
-				   subclass, NULL, _RET_IP_, NULL);
+				   subclass, NULL, _RET_IP_, NULL, 0);
 }
 EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
 
@@ -644,7 +644,7 @@ mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
 {
 	might_sleep();
 	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
-				   subclass, NULL, _RET_IP_, NULL);
+				   subclass, NULL, _RET_IP_, NULL, 0);
 }
 
 EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
@@ -682,7 +682,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 
 	might_sleep();
 	ret =  __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
-				   0, &ctx->dep_map, _RET_IP_, ctx);
+				   0, &ctx->dep_map, _RET_IP_, ctx, 1);
 	if (!ret && ctx->acquired > 1)
 		return ww_mutex_deadlock_injection(lock, ctx);
 
@@ -697,7 +697,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 
 	might_sleep();
 	ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
-				  0, &ctx->dep_map, _RET_IP_, ctx);
+				  0, &ctx->dep_map, _RET_IP_, ctx, 1);
 
 	if (!ret && ctx->acquired > 1)
 		return ww_mutex_deadlock_injection(lock, ctx);
@@ -809,36 +809,36 @@ __mutex_lock_slowpath(atomic_t *lock_count)
 	struct mutex *lock = container_of(lock_count, struct mutex, count);
 
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
-			    NULL, _RET_IP_, NULL);
+			    NULL, _RET_IP_, NULL, 0);
 }
 
 static noinline int __sched
 __mutex_lock_killable_slowpath(struct mutex *lock)
 {
 	return __mutex_lock_common(lock, TASK_KILLABLE, 0,
-				   NULL, _RET_IP_, NULL);
+				   NULL, _RET_IP_, NULL, 0);
 }
 
 static noinline int __sched
 __mutex_lock_interruptible_slowpath(struct mutex *lock)
 {
 	return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
-				   NULL, _RET_IP_, NULL);
+				   NULL, _RET_IP_, NULL, 0);
 }
 
 static noinline int __sched
 __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 {
 	return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
-				   NULL, _RET_IP_, ctx);
+				   NULL, _RET_IP_, ctx, 1);
 }
 
 static noinline int __sched
 __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
 					    struct ww_acquire_ctx *ctx)
 {
 	return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
-				   NULL, _RET_IP_, ctx);
+				   NULL, _RET_IP_, ctx, 1);
 }
 
 #endif