From b11496783537d67d6e23bb733080c513dfa050ce Mon Sep 17 00:00:00 2001 From: Chuansheng Liu Date: Fri, 7 Jun 2013 10:08:39 +1000 Subject: [PATCH] smp: Give WARN()ing when calling smp_call_function_many()/single() in serving irq 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 Cc: Ingo Molnar Cc: Peter Zijlstra Tested-by: Fengguang Wu Cc: Lai Jiangshan Signed-off-by: Andrew Morton --- include/linux/hardirq.h | 5 +++++ kernel/smp.c | 11 +++++++---- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 05bcc0903766..ecc8e01f492a 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 4dba0f7b72ad..97084cfc61ca 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -12,6 +12,7 @@ #include #include #include +#include #include "smpboot.h" @@ -240,8 +241,9 @@ 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); @@ -378,8 +380,9 @@ 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); -- 2.39.5