linux-kernel - [tip:core/ipi] generic-ipi: eliminate spurious pointless WARN

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Message-ID: <tip-6a09dfa870ba0ed21b1124539968a36b42660661@git.kernel.org>
Date:	Fri, 13 Mar 2009 01:39:23 GMT
From:	Jan Beulich <jbeulich@...ell.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	jbeulich@...ell.com, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:core/ipi] generic-ipi: eliminate spurious pointless WARN_ON()s

Commit-ID:  6a09dfa870ba0ed21b1124539968a36b42660661
Gitweb:     http://git.kernel.org/tip/6a09dfa870ba0ed21b1124539968a36b42660661
Author:     Jan Beulich <jbeulich@...ell.com>
AuthorDate: Thu, 12 Mar 2009 13:21:50 +0000
Commit:     Ingo Molnar <mingo@...e.hu>
CommitDate: Fri, 13 Mar 2009 02:14:41 +0100

generic-ipi: eliminate spurious pointless WARN_ON()s

Namely during early boot, the panic() or BUG() paths may end up in
smp_call_function_*() with just a single online CPU. In that situation
the warnings generated are not only meaningless, but also result in
relevant output being cluttered.

Therefore, defer the WARN_ON() checks until after the (unaffected from
the problem that is being attempted to be detected here) cases have
been handled.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
LKML-Reference: <49B91A7E.76E4.0078.0@...ell.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/smp.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 7ad2262..37b90a9 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -284,9 +284,6 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 	 */
 	this_cpu = get_cpu();
 
-	/* Can deadlock when called with interrupts disabled */
-	WARN_ON(irqs_disabled());
-
 	if (cpu == this_cpu) {
 		local_irq_save(flags);
 		func(info);
@@ -295,6 +292,9 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 		if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
 			struct call_single_data *data = &d;
 
+			/* Can deadlock when called with interrupts disabled */
+			WARN_ON(irqs_disabled());
+
 			if (!wait)
 				data = &__get_cpu_var(csd_data);
 
@@ -364,9 +364,6 @@ void smp_call_function_many(const struct cpumask *mask,
 	unsigned long flags;
 	int cpu, next_cpu, this_cpu = smp_processor_id();
 
-	/* Can deadlock when called with interrupts disabled */
-	WARN_ON(irqs_disabled());
-
 	/* So, what's a CPU they want? Ignoring this one. */
 	cpu = cpumask_first_and(mask, cpu_online_mask);
 	if (cpu == this_cpu)
@@ -387,6 +384,9 @@ void smp_call_function_many(const struct cpumask *mask,
 		return;
 	}
 
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
 	data = &__get_cpu_var(cfd_data);
 	csd_lock(&data->csd);
 
--
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