linux-kernel - [tip:core/locking] smp: Give WARN()ing if in_interrupt() when calling smp_call_function

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Date:	Wed, 6 Feb 2013 05:42:58 -0800
From:	tip-bot for Chuansheng Liu <chuansheng.liu@...el.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	a.p.zijlstra@...llo.nl, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, tglx@...utronix.de,
	chuansheng.liu@...el.com
Subject: [tip:core/locking] smp: Give WARN()ing if in_interrupt()
  when calling smp_call_function_many()/single()

Commit-ID:  b29f39c7c3e75a741a7da88244ec707f293ec04c
Gitweb:     http://git.kernel.org/tip/b29f39c7c3e75a741a7da88244ec707f293ec04c
Author:     Chuansheng Liu <chuansheng.liu@...el.com>
AuthorDate: Wed, 6 Feb 2013 23:18:21 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 6 Feb 2013 12:00:30 +0100

smp: Give WARN()ing if in_interrupt() when calling smp_call_function_many()/single()

Currently the functions smp_call_function_many()/single() will
give a WARN()ing only in the case of irqs_disabled(), but that
check is not enough to guarantee execution of the SMP
cross-calls.

In many other cases such as softirq handling/interrupt handling,
the two APIs still can not be called, just as the
smp_call_function_many() comments say:

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

There is a real case for softirq DEADLOCK case:

CPUA                            CPUB
                                spin_lock(&spinlock)
                                Any irq coming, call the irq handler
                                irq_exit()
spin_lock_irq(&spinlock)
<== Blocking here due to
CPUB hold it
                                  __do_softirq()
                                    run_timer_softirq()
                                      timer_cb()
                                        call smp_call_function_many()
                                          send IPI interrupt to CPUA
                                            wait_csd()

Then both CPUA and CPUB will be deadlocked here.

So we should give a warning in the in_interrupt() case as well.

Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
Cc: jun.zhang@...el.com
Cc: peterz@...radead.org
Cc: jbeulich@...e.com
Cc: paulmck@...ux.vnet.ibm.com
Cc: mina86@...a86.org
Cc: srivatsa.bhat@...ux.vnet.ibm.com
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1360163901.24670.13.camel@cliu38-desktop-build
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/smp.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 29dd40a..fec45aa 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -12,6 +12,7 @@
 #include <linux/gfp.h>
 #include <linux/smp.h>
 #include <linux/cpu.h>
+#include <linux/hardirq.h>
 
 #include "smpboot.h"
 
@@ -318,7 +319,7 @@ 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) && (irqs_disabled() || in_interrupt())
 		     && !oops_in_progress);
 
 	if (cpu == this_cpu) {
@@ -416,8 +417,9 @@ void __smp_call_function_single(int cpu, struct call_single_data *data,
 	 * send smp call function interrupt to this cpu and as such deadlocks
 	 * can't happen.
 	 */
-	WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled()
-		     && !oops_in_progress);
+	WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait
+			&& (irqs_disabled() || in_interrupt())
+			&& !oops_in_progress);
 
 	if (cpu == this_cpu) {
 		local_irq_save(flags);
--
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