[PATCH] smp: give WARN in case of in_interrupt() when callingsmp_call_function_many/single

[Chuansheng Liu]

Currently, in function smp_call_function_many/single, it will give WARN just in case
of irqs_disabled(), but it is not enough.

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 said:
 * 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 DEADLOCK here.

So we should give WARN in case of in_interrupt(), not only irqd_disabled().

Signed-off-by: liu chuansheng <chuansheng.liu@xxxxxxxxx>
---
 kernel/smp.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 69f38bd..a2f0b2c 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"
 
@@ -323,7 +324,7 @@ 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) {
@@ -421,8 +422,9 @@ 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);
-- 
1.7.0.4



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