[PATCH] freezer: Check frozen() before freezing() in freeze_task()

[Samuel Wu <wusamuel@google.com>]

During the freeze stage of suspend, there are multiple passes over the
same list of tasks. Each pass tries to freeze non-frozen tasks, meaning
that the number of frozen tasks increase monotonically, and that each
subsequent pass will mostly be iterating over frozen tasks. Therefore,
it is faster to *first* check that a task is frozen before other checks,
especially since the frozen check is computationally trivial.

Check frozen(p) before !freezing(p) to short circuit the more expensive
freezing_slow_path() calls, while retaining identical return semantics.

On a v7.3 Pixel 9 device, this consistently reduces freeze_processes
latency by ~10% (~4.5 ms).

Signed-off-by: Samuel Wu <wusamuel@google.com>
---
 kernel/freezer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/freezer.c b/kernel/freezer.c
index a76bf957fb32..1adf09321389 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -166,7 +166,7 @@ bool freeze_task(struct task_struct *p)
 	unsigned long flags;
 
 	spin_lock_irqsave(&freezer_lock, flags);
-	if (!freezing(p) || frozen(p) || __freeze_task(p)) {
+	if (frozen(p) || !freezing(p) || __freeze_task(p)) {
 		spin_unlock_irqrestore(&freezer_lock, flags);
 		return false;
 	}
-- 
2.56.0.679.gc527c65306-goog