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authorJason Low <jason.low2@hp.com>2015-04-08 12:39:19 -0700
committerIngo Molnar <mingo@kernel.org>2015-04-09 08:10:23 +0200
commit01ac33c1f907b366dcc50551316b372f1519cca9 (patch)
tree3acec01dacf54ca648dda938b21fe5a0626f9e5b /kernel/locking
parent7bd3e239d6c6d1cad276e8f130b386df4234dcd7 (diff)
locking/mutex: Further simplify mutex_spin_on_owner()
Similar to what Linus suggested for rwsem_spin_on_owner(), in mutex_spin_on_owner() instead of having while (true) and breaking out of the spin loop on lock->owner != owner, we can have the loop directly check for while (lock->owner == owner) to improve the readability of the code. It also shrinks the code a bit: text data bss dec hex filename 3721 0 0 3721 e89 mutex.o.before 3705 0 0 3705 e79 mutex.o.after Signed-off-by: Jason Low <jason.low2@hp.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Link: http://lkml.kernel.org/r/1428521960-5268-2-git-send-email-jason.low2@hp.com [ Added code generation info. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/mutex.c14
1 files changed, 4 insertions, 10 deletions
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 16b2d3cc88b0..4cccea6b8934 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -224,20 +224,14 @@ ww_mutex_set_context_slowpath(struct ww_mutex *lock,
static noinline
bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
{
- bool ret;
+ bool ret = true;
rcu_read_lock();
- while (true) {
- /* Return success when the lock owner changed */
- if (lock->owner != owner) {
- ret = true;
- break;
- }
-
+ while (lock->owner == owner) {
/*
* Ensure we emit the owner->on_cpu, dereference _after_
- * checking lock->owner still matches owner, if that fails,
- * owner might point to free()d memory, if it still matches,
+ * checking lock->owner still matches owner. If that fails,
+ * owner might point to freed memory. If it still matches,
* the rcu_read_lock() ensures the memory stays valid.
*/
barrier();