netdev - [PATCH 2/9] ipvs: Fix possible deadlock in estimator code

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Date:	Sun, 10 Aug 2008 11:07:32 +0000
From:	sven.wegener@...aler.net
To:	wensong@...ux-vs.org, horms@...ge.net.au, ja@....bg
Cc:	netdev@...r.kernel.org, lvs-devel@...r.kernel.org
Subject: [PATCH 2/9] ipvs: Fix possible deadlock in estimator code

From: Sven Wegener <sven.wegener@...aler.net>

There is a slight chance for a deadlock in the estimator code. We can't call
del_timer_sync() while holding our lock, as the timer might be active and
spinning for the lock on another cpu. Work around this issue by using
try_to_del_timer_sync() and releasing the lock. We could actually delete the
timer outside of our lock, as the add and kill functions are only every called
from userspace via [gs]etsockopt() and are serialized by a mutex, but better
make this explicit.

Signed-off-by: Sven Wegener <sven.wegener@...aler.net>
Cc: stable <stable@...nel.org>
---
 net/ipv4/ipvs/ip_vs_est.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ipvs/ip_vs_est.c b/net/ipv4/ipvs/ip_vs_est.c
index bc04eed..1d6e58e 100644
--- a/net/ipv4/ipvs/ip_vs_est.c
+++ b/net/ipv4/ipvs/ip_vs_est.c
@@ -170,8 +170,11 @@ void ip_vs_kill_estimator(struct ip_vs_stats *stats)
 		kfree(est);
 		killed++;
 	}
-	if (killed && est_list == NULL)
-		del_timer_sync(&est_timer);
+	while (killed && !est_list && try_to_del_timer_sync(&est_timer) < 0) {
+		write_unlock_bh(&est_lock);
+		cpu_relax();
+		write_lock_bh(&est_lock);
+	}
 	write_unlock_bh(&est_lock);
 }
 
-- 
1.5.6.4

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