linux-kernel - [PATCH 2/2] mm: Add comment explaining task state setting in bdi_forker

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Message-Id: <1315004059-9844-3-git-send-email-jack@suse.cz>
Date:	Sat,  3 Sep 2011 00:54:19 +0200
From:	Jan Kara <jack@...e.cz>
To:	Jens Axboe <jaxboe@...ionio.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 2/2] mm: Add comment explaining task state setting in bdi_forker_thread()

CC: Wu Fengguang <fengguang.wu@...el.com>
CC: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Jan Kara <jack@...e.cz>
---
 mm/backing-dev.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 94a047b..a87da52 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -401,6 +401,13 @@ static int bdi_forker_thread(void *ptr)
 		}
 
 		spin_lock_bh(&bdi_lock);
+		/*
+		 * In the following loop we are going to check whether we have
+		 * some work to do without any synchronization with tasks
+		 * waking us up to do work for them. So we have to set task
+		 * state already here so that we don't miss wakeups coming
+		 * after we verify some condition.
+		 */
 		set_current_state(TASK_INTERRUPTIBLE);
 
 		list_for_each_entry(bdi, &bdi_list, bdi_list) {
-- 
1.7.1

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