mutex: Avoid gcc version dependent __builtin_constant_p() usage

Commit 040a0a37 ("mutex: Add support for wound/wait style locks")
used "!__builtin_constant_p(p == NULL)" but gcc 3.x cannot
handle such expression correctly, leading to boot failure when
built with CONFIG_DEBUG_MUTEXES=y.

Fix it by explicitly passing a bool which tells whether p != NULL
or not.

[ PeterZ: This is a sad patch, but provided it actually generates
          similar code I suppose its the best we can do bar whole
	  sale deprecating gcc-3. ]

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Cc: peterz@infradead.org
Cc: imirkin@alum.mit.edu
Cc: daniel.vetter@ffwll.ch
Cc: robdclark@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/201310171945.AGB17114.FSQVtHOJFOOFML@I-love.SAKURA.ne.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 16 insertions, 16 deletions

diff --git a/kernel/mutex.c b/kernel/mutex.c
index 6d647aedffea..d24105b1b794 100644
--- a/kernel/mutex.c
+++ b/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 @@ slowpath:
                         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 @@ skip_wait:
         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);
@@ -809,28 +809,28 @@ __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
@@ -838,7 +838,7 @@ __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