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 nmi, hardirq or softirq context as well.
Moreover, adding one new macro in_serving_irq() which indicates
we are processing nmi, hardirq or sofirq.
Signed-off-by: liu chuansheng <chuansheng....@intel.com>
---
include/linux/hardirq.h | 5 +++++
kernel/smp.c | 10 ++++++----
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 624ef3f..e07663f 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -94,6 +94,11 @@
*/
#define in_nmi() (preempt_count() & NMI_MASK)
+/*
+ * Are we in nmi,irq context, or softirq context?
+ */
+#define in_serving_irq() (in_nmi() || in_irq() || in_serving_softirq())
+
#if defined(CONFIG_PREEMPT_COUNT)
# define PREEMPT_CHECK_OFFSET 1
#else
diff --git a/kernel/smp.c b/kernel/smp.c
index 69f38bd..ba43dd7 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -323,8 +323,9 @@ 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()
- && !oops_in_progress);
+ WARN_ON_ONCE(cpu_online(this_cpu)
+ && (irqs_disabled() || in_serving_irq())
+ && !oops_in_progress);
if (cpu == this_cpu) {
local_irq_save(flags);
@@ -462,8 +463,9 @@ void smp_call_function_many(const struct cpumask *mask,
* send smp call function interrupt to this cpu and as such deadlocks
* can't happen.
*/
- WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
- && !oops_in_progress && !early_boot_irqs_disabled);
+ WARN_ON_ONCE(cpu_online(this_cpu)
+ && (irqs_disabled() || in_serving_irq())
+ && !oops_in_progress && !early_boot_irqs_disabled);
/* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
cpu = cpumask_first_and(mask, cpu_online_mask);
--
1.7.0.4
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