linux-kernel - [PATCH 01/19] freezer: don't get over-anxious while waiting

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Date:	Thu,  1 Oct 2009 17:09:00 +0900
From:	Tejun Heo <tj@...nel.org>
To:	jeff@...zik.org, mingo@...e.hu, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, jens.axboe@...cle.com,
	rusty@...tcorp.com.au, cl@...ux-foundation.org,
	dhowells@...hat.com, arjan@...ux.intel.com
Cc:	Tejun Heo <tj@...nel.org>
Subject: [PATCH 01/19] freezer: don't get over-anxious while waiting

Freezing isn't exactly the most latency sensitive operation and
there's no reason to burn cpu cycles and power waiting for it to
complete.  msleep(10) instead of yield().  This should improve
reliability of emergency hibernation.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/power/process.c |   13 +++++++++----
 1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/kernel/power/process.c b/kernel/power/process.c
index cc2e553..9d26a0a 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -41,7 +41,7 @@ static int try_to_freeze_tasks(bool sig_only)
 	do_gettimeofday(&start);
 
 	end_time = jiffies + TIMEOUT;
-	do {
+	while (true) {
 		todo = 0;
 		read_lock(&tasklist_lock);
 		do_each_thread(g, p) {
@@ -62,10 +62,15 @@ static int try_to_freeze_tasks(bool sig_only)
 				todo++;
 		} while_each_thread(g, p);
 		read_unlock(&tasklist_lock);
-		yield();			/* Yield is okay here */
-		if (time_after(jiffies, end_time))
+		if (!todo || time_after(jiffies, end_time))
 			break;
-	} while (todo);
+
+		/*
+		 * We need to retry.  There's no reason to be
+		 * over-anxious about it and waste power.
+		 */
+		msleep(10);
+	}
 
 	do_gettimeofday(&end);
 	elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
-- 
1.6.4.2

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