linux-kernel - [PATCH] netconsole: Disable softirqs in write

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Date:	Wed, 19 Nov 2008 08:41:06 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	David Miller <davem@...emloft.net>, Jeff Garzik <jeff@...zik.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Johannes Berg <johannes@...solutions.net>,
	Ferenc Wagner <wferi@...f.hu>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] netconsole: Disable softirqs in write_msg()

This report: http://marc.info/?l=linux-netdev&m=122599341430090&w=2
shows local_bh_enable() is used in the wrong context (irqs disabled).
It happens when a usual network path is called by netconsole, which
simply turns off hardirqs around this all.

This patch additionally disables softirqs to avoid possibility of
enabling bh and calling do_softirq() with hardirqs disabled.

Reported-by: Ferenc Wagner <wferi@...f.hu>
Signed-off-by: Jarek Poplawski <jarkao2@...il.com>
---

 drivers/net/netconsole.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index d304d38..f6ecad8 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -702,6 +702,8 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 	if (list_empty(&target_list))
 		return;
 
+	/* Avoid enabling softirqs with hardirqs disabled */
+	local_bh_disable();
 	spin_lock_irqsave(&target_list_lock, flags);
 	list_for_each_entry(nt, &target_list, list) {
 		netconsole_target_get(nt);
@@ -723,6 +725,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 		netconsole_target_put(nt);
 	}
 	spin_unlock_irqrestore(&target_list_lock, flags);
+	local_bh_enable();
 }
 
 static struct console netconsole = {
--
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