linux-kernel - [34-longterm 064/209] latencytop: fix per task accumulator

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Message-Id: <1302803039-9400-65-git-send-email-paul.gortmaker@windriver.com>
Date:	Thu, 14 Apr 2011 13:41:34 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Ken Chen <kenchen@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 064/209] latencytop: fix per task accumulator

From: Ken Chen <kenchen@...gle.com>

  =====================================================================
  | This is a commit scheduled for the next v2.6.34 longterm release. |
  | If you see a problem with using this for longterm, please comment.|
  =====================================================================

commit 38715258aa2e8cd94bd4aafadc544e5104efd551 upstream.

Per task latencytop accumulator prematurely terminates due to erroneous
placement of latency_record_count.  It should be incremented whenever a
new record is allocated instead of increment on every latencytop event.

Also fix search iterator to only search known record events instead of
blindly searching all pre-allocated space.

Signed-off-by: Ken Chen <kenchen@...gle.com>
Reviewed-by: Arjan van de Ven <arjan@...radead.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 kernel/latencytop.c |   17 ++++++++---------
 1 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/kernel/latencytop.c b/kernel/latencytop.c
index 877fb30..17110a4 100644
--- a/kernel/latencytop.c
+++ b/kernel/latencytop.c
@@ -194,14 +194,7 @@ __account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
 
 	account_global_scheduler_latency(tsk, &lat);
 
-	/*
-	 * short term hack; if we're > 32 we stop; future we recycle:
-	 */
-	tsk->latency_record_count++;
-	if (tsk->latency_record_count >= LT_SAVECOUNT)
-		goto out_unlock;
-
-	for (i = 0; i < LT_SAVECOUNT; i++) {
+	for (i = 0; i < tsk->latency_record_count; i++) {
 		struct latency_record *mylat;
 		int same = 1;
 
@@ -227,8 +220,14 @@ __account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
 		}
 	}
 
+	/*
+	 * short term hack; if we're > 32 we stop; future we recycle:
+	 */
+	if (tsk->latency_record_count >= LT_SAVECOUNT)
+		goto out_unlock;
+
 	/* Allocated a new one: */
-	i = tsk->latency_record_count;
+	i = tsk->latency_record_count++;
 	memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
 
 out_unlock:
-- 
1.7.4.4

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