linux-kernel - [PATCH 3.13.y-ckt 088/121] nfs: Don't busy-wait on SIGKILL in __nfs_iocounter

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Message-Id: <1417548000-1794-89-git-send-email-kamal@canonical.com>
Date:	Tue,  2 Dec 2014 11:19:27 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	David Jeffery <djeffery@...hat.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Moritz Mühlenhoff <muehlenhoff@...vention.de>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13.y-ckt 088/121] nfs: Don't busy-wait on SIGKILL in __nfs_iocounter_wait

3.13.11-ckt12 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Jeffery <djeffery@...hat.com>

commit 92a56555bd576c61b27a5cab9f38a33a1e9a1df5 upstream.

If a SIGKILL is sent to a task waiting in __nfs_iocounter_wait,
it will busy-wait or soft lockup in its while loop.
nfs_wait_bit_killable won't sleep, and the loop won't exit on
the error return.

Stop the busy-wait by breaking out of the loop when
nfs_wait_bit_killable returns an error.

Signed-off-by: David Jeffery <djeffery@...hat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
[ kamal: backport to 3.13-stable: context ]
Cc: Moritz Mühlenhoff <muehlenhoff@...vention.de>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 fs/nfs/pagelist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 2ffebf2..27d7f27 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -113,7 +113,7 @@ __nfs_iocounter_wait(struct nfs_io_counter *c)
 		if (atomic_read(&c->io_count) == 0)
 			break;
 		ret = nfs_wait_bit_killable(&c->flags);
-	} while (atomic_read(&c->io_count) != 0);
+	} while (atomic_read(&c->io_count) != 0 && !ret);
 	finish_wait(wq, &q.wait);
 	return ret;
 }
-- 
1.9.1

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