linux-kernel - [PATCH] softirq: Fix warnings triggered by netconsole

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Message-ID: <20081119084125.GB6699@ff.dom.local>
Date:	Wed, 19 Nov 2008 08:41:26 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Johannes Berg <johannes@...solutions.net>,
	David Miller <davem@...emloft.net>,
	Ferenc Wagner <wferi@...f.hu>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] softirq: Fix warnings triggered by netconsole

Consider netconsole case as special in local_bh_enable()/_disable().
This patch skips in_irq() and irqs_disabled() warnings for NETPOLL
configs when it's safe wrt. do_softirq().

Reported-by: Ferenc Wagner <wferi@...f.hu>
Signed-off-by: Jarek Poplawski <jarkao2@...il.com>
---
[apply on top of my first softirq patch in this thread]

diff -Nurp a/kernel/softirq.c b/kernel/softirq.c
--- a/kernel/softirq.c	2008-11-19 07:33:23.000000000 +0000
+++ b/kernel/softirq.c	2008-11-19 07:26:28.000000000 +0000
@@ -76,7 +76,12 @@ static void __local_bh_disable(unsigned 
 {
 	unsigned long flags;
 
+#ifdef CONFIG_NETPOLL
+	if (!softirq_count())
+		WARN_ON_ONCE(in_irq());
+#else
 	WARN_ON_ONCE(in_irq());
+#endif
 
 	raw_local_irq_save(flags);
 	add_preempt_count(SOFTIRQ_OFFSET);
@@ -138,7 +143,16 @@ static inline void _local_bh_enable_ip(u
 #ifdef CONFIG_TRACE_IRQFLAGS
 	unsigned long flags;
 #endif
+#ifdef CONFIG_NETPOLL
+	/*
+	 * Special-case - netconsole runs network code with all interrupts
+	 * disabled. Warn only if it can be really dangerous:
+	 */
+	if (softirq_count() == SOFTIRQ_OFFSET)
+		WARN_ON_ONCE(in_irq() || irqs_disabled());
+#else
 	WARN_ON_ONCE(in_irq() || irqs_disabled());
+#endif
 #ifdef CONFIG_TRACE_IRQFLAGS
 	local_irq_save(flags);
 #endif
--
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