From: Andrew Morton <akpm@osdl.org>
Date: Thu, 7 Dec 2006 04:38:16 +0000 (-0800)
Subject: [PATCH] smp_call_function_single() check that local interrupts are enabled
X-Git-Tag: v2.6.20-rc1~145^2^2~137
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=a38a44c1a93078fc5fadc4ac2df8dea4697069e2;p=linux-2.6-omap-h63xx.git

[PATCH] smp_call_function_single() check that local interrupts are enabled

smp_call_function_single() can deadlock if the caller disabled local
interrupts (the target CPU could be spinning on call_lock).  Check for that.

Why on earth do these functions use spin_lock_bh()??

Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Cc: Andi Kleen <ak@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/arch/i386/kernel/smp.c b/arch/i386/kernel/smp.c
index 31e5c6573aa..9827cf927ec 100644
--- a/arch/i386/kernel/smp.c
+++ b/arch/i386/kernel/smp.c
@@ -699,6 +699,10 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 		put_cpu();
 		return -EBUSY;
 	}
+
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	spin_lock_bh(&call_lock);
 	__smp_call_function_single(cpu, func, info, nonatomic, wait);
 	spin_unlock_bh(&call_lock);
diff --git a/arch/x86_64/kernel/smp.c b/arch/x86_64/kernel/smp.c
index 9f74c883568..32f4d7e2a06 100644
--- a/arch/x86_64/kernel/smp.c
+++ b/arch/x86_64/kernel/smp.c
@@ -379,6 +379,10 @@ int smp_call_function_single (int cpu, void (*func) (void *info), void *info,
 		put_cpu();
 		return 0;
 	}
+
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	spin_lock_bh(&call_lock);
 	__smp_call_function_single(cpu, func, info, nonatomic, wait);
 	spin_unlock_bh(&call_lock);