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2.6.6-rc3 Warn when smp_call_function() is called with interrupts disabled

PATCH New Keith Owens 1 participant 1 message May 3, 2004

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MIPS s390 SuperH User-mode Linux (UML) +2 more subsystems
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Keith Owens

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PATCH 1/1 2.6.6-rc3 Warn when smp_call_function() is called with interrupts disabled

Almost every architecture has a comment above smp_call_function()

* You must not call this function with disabled interrupts or from a
* hardware interrupt handler or from a bottom half handler.

I have not seen any problems with calling smp_call_function() from a bottom half handler, but calling it with interrupts disabled can definitely deadlock. This bug is hard to reproduce and even harder to debug.

CPU A CPU B
Disable interrupts
smp_call_function()
Take call_lock
Send IPIs
Wait for all cpus to acknowledge IPI CPU A has not responded, spin waiting for cpu A to respond, holding call_lock
smp_call_function()
Spin waiting for call_lock
Deadlock Deadlock

Change all smp_call_function() to WARN_ON(irqs_disabled()). It should be BUG_ON() but some buggy code like SCSI sg will break with BUG_ON, so just warn for now. Change it to BUG_ON after the buggy code has been fixed.

Tested on ia64 and i386. It was even tested on UP, just for akpm ;)

arch/alpha/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/alpha/kernel/smp.c
===================================================================
@@ -820,6 +820,9 @@
 	unsigned long timeout;
 	int num_cpus_to_call;
 	
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	data.wait = wait;
arch/i386/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/i386/kernel/smp.c
===================================================================
@@ -519,6 +519,9 @@
 	if (!cpus)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.started, 0);
arch/i386/mach-voyager/voyager_smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/i386/mach-voyager/voyager_smp.c
===================================================================
@@ -1106,6 +1106,9 @@
 	if (!mask)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	data.started = mask;
arch/ia64/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/ia64/kernel/smp.c
===================================================================
@@ -308,6 +308,9 @@
 	if (!cpus)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.started, 0);
arch/mips/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/mips/kernel/smp.c
===================================================================
@@ -151,6 +151,9 @@
 	if (!cpus)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.started, 0);
arch/parisc/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/parisc/kernel/smp.c
===================================================================
@@ -327,6 +327,9 @@
 	struct smp_call_struct data;
 	unsigned long timeout;
 	static spinlock_t lock = SPIN_LOCK_UNLOCKED;
+
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
 	
 	data.func = func;
 	data.info = info;
arch/ppc/kernel/smp.c +2 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/ppc/kernel/smp.c
===================================================================
@@ -211,6 +211,8 @@
            bitmask. --RR */
 	if (num_online_cpus() <= 1)
 		return 0;
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
 	return __smp_call_function(func, info, wait, MSG_ALL_BUT_SELF);
 }
arch/ppc64/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/ppc64/kernel/smp.c
===================================================================
@@ -692,6 +692,9 @@
 	int ret = -1, cpus;
 	unsigned long timeout;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.started, 0);
arch/s390/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/s390/kernel/smp.c
===================================================================
@@ -127,6 +127,9 @@
 	if (cpus <= 0)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.started, 0);
arch/sh/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/sh/kernel/smp.c
===================================================================
@@ -181,6 +181,9 @@
 	if (nr_cpus < 2)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	spin_lock(&smp_fn_call.lock);
 
 	atomic_set(&smp_fn_call.finished, 0);
arch/sparc64/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/sparc64/kernel/smp.c
===================================================================
@@ -598,6 +598,9 @@
 	if (!cpus)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.finished, 0);
arch/um/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/um/kernel/smp.c
===================================================================
@@ -266,6 +266,9 @@
 	if (!cpus)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	spin_lock_bh(&call_lock);
 	atomic_set(&scf_started, 0);
 	atomic_set(&scf_finished, 0);
arch/x86_64/kernel/smp.c +3 -0
Index: 2.6.6-rc3-warn-smp_call_function/arch/x86_64/kernel/smp.c
===================================================================
@@ -404,6 +404,9 @@
 	if (!cpus)
 		return 0;
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data.func = func;
 	data.info = info;
 	atomic_set(&data.started, 0);