linux-kernel - [PATCHv4 04/14] writeback: do not lose wake-ups in the forker thread

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1279897554-1526-5-git-send-email-dedekind1@gmail.com>
Date:	Fri, 23 Jul 2010 18:05:44 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCHv4 04/14] writeback: do not lose wake-ups in the forker thread - 2

From: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>

Currently, if someone submits jobs for the default bdi, we can lose wake-up
events. E.g., this can happen if 'bdi_queue_work()' is called when
'bdi_forker_thread()' is executing code after 'wb_do_writeback(me, 0)', but
before 'set_current_state(TASK_INTERRUPTIBLE)'.

This situation is unlikely, and the result is not very severe - we'll just
delay the execution of the work, but this is still not very nice.

This patch fixes the issue by checking whether the default bdi has works before
the forker thread goes sleep.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 mm/backing-dev.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index b1dc2d4..72e6eb9 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -358,6 +358,10 @@ static int bdi_forker_thread(void *ptr)
 			bdi_add_default_flusher_thread(bdi);
 		}
 
+		/* Keep working if default bdi still has things to do */
+		if (!list_empty(&me->bdi->work_list))
+			__set_current_state(TASK_RUNNING);
+
 		if (list_empty(&bdi_pending_list)) {
 			unsigned long wait;
 
-- 
1.7.1.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/