linux-kernel - [RFC PATCH 08/15] smp: Don't warn if irq are disabled but we don't wait for the ipi

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Date:	Mon, 20 Dec 2010 16:24:15 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Anton Blanchard <anton@....ibm.com>,
	Tim Pepper <lnxninja@...ux.vnet.ibm.com>
Subject: [RFC PATCH 08/15] smp: Don't warn if irq are disabled but we don't wait for the ipi

The comment in smp_call_function_single() says it wants the irqs
to be enabled otherwise it may deadlock.

I can't find the reason for that though, except if we had to wait
for a self triggered IPI but we execute the local IPI by just
calling the function in place.

In doubt, only suppress the warning if we are not waiting for the
IPI to complete as it should really not raise any deadlock.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Anton Blanchard <anton@....ibm.com>
Cc: Tim Pepper <lnxninja@...ux.vnet.ibm.com>
---
 kernel/smp.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 12ed8b0..886a406 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -289,7 +289,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
 	 * send smp call function interrupt to this cpu and as such deadlocks
 	 * can't happen.
 	 */
-	WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
+	WARN_ON_ONCE(cpu_online(this_cpu) && wait && irqs_disabled()
 		     && !oops_in_progress);
 
 	if (cpu == this_cpu) {
-- 
1.7.3.2

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