This patch applies on top of tip.
-------------------------------------------------------------------
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). This improves the
readability of the code.
Signed-off-by: Jason Low <jason.l...@hp.com>
---
kernel/locking/mutex.c | 17 +++++------------
1 files changed, 5 insertions(+), 12 deletions(-)
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 16b2d3c..1c3b7c5 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -224,16 +224,8 @@ 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;
-
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,
@@ -242,16 +234,17 @@ bool mutex_spin_on_owner(struct mutex *lock, struct
task_struct *owner)
*/
barrier();
+ /* Stop spinning when need_resched or owner is not running. */
if (!owner->on_cpu || need_resched()) {
- ret = false;
- break;
+ rcu_read_unlock();
+ return false;
}
cpu_relax_lowlatency();
}
rcu_read_unlock();
- return ret;
+ return true;
}
/*
--
1.7.2.5
--
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