Commit-ID: 01ac33c1f907b366dcc50551316b372f1519cca9 Gitweb: http://git.kernel.org/tip/01ac33c1f907b366dcc50551316b372f1519cca9 Author: Jason Low <jason.l...@hp.com> AuthorDate: Wed, 8 Apr 2015 12:39:19 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 9 Apr 2015 08:10:23 +0200
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.l...@hp.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Aswin Chandramouleeswaran <as...@hp.com> Cc: Davidlohr Bueso <d...@stgolabs.net> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Tim Chen <tim.c.c...@linux.intel.com> Link: http://lkml.kernel.org/r/1428521960-5268-2-git-send-email-jason.l...@hp.com [ Added code generation info. ] Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/locking/mutex.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 16b2d3c..4cccea6 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(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
