From ddb7fec09b32ec61e428e7e882b6821a10d3df3f Mon Sep 17 00:00:00 2001
From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Date: Thu, 22 May 2014 10:44:05 +1000
Subject: [PATCH] 
 smp-print-more-useful-debug-info-upon-receiving-ipi-on-an-offline-cpu-v5

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <mgalbraith@suse.de>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 kernel/smp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index f864921fc82c..306f8180b0d5 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -195,13 +195,15 @@ void generic_smp_call_function_single_interrupt(void)
 	 */
 	if (unlikely(!cpu_online(smp_processor_id()) && !warned)) {
 		warned = true;
-		WARN_ON(1);
+		WARN(1, "IPI on offline CPU %d\n", smp_processor_id());
+
 		/*
 		 * We don't have to use the _safe() variant here
 		 * because we are not invoking the IPI handlers yet.
 		 */
 		llist_for_each_entry(csd, entry, llist)
-			pr_warn("SMP IPI Payload: %pS \n", csd->func);
+			pr_warn("IPI callback %pS sent to offline CPU\n",
+				csd->func);
 	}
 
 	llist_for_each_entry_safe(csd, csd_next, entry, llist) {
-- 
2.39.5