Messages in this thread Patch in this message | | | Subject | [PATCH] smp: Give WARN()ing when calling smp_call_function_many()/single() in serving irq | From | Chuansheng Liu <> | Date | Sat, 16 Feb 2013 21:57:55 +0800 |
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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.liu@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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