smp: Warn on function calls from softirq context
It's clearly documented that smp function calls cannot be invoked from
softirq handling context. Unfortunately nothing enforces that or emits a
warning.
A single function call can be invoked from softirq context only via
smp_call_function_single_async().
The only legit context is task context, so add a warning to that effect.
Reported-by: luferry <luferry@163.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190718160601.GP3402@hirez.programming.kicks-ass.net
diff --git a/kernel/smp.c b/kernel/smp.c
index 616d4d1..7dbcb40 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -291,6 +291,14 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
&& !oops_in_progress);
+ /*
+ * When @wait we can deadlock when we interrupt between llist_add() and
+ * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
+ * csd_lock() on because the interrupt context uses the same csd
+ * storage.
+ */
+ WARN_ON_ONCE(!in_task());
+
csd = &csd_stack;
if (!wait) {
csd = this_cpu_ptr(&csd_data);
@@ -416,6 +424,14 @@ void smp_call_function_many(const struct cpumask *mask,
WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
&& !oops_in_progress && !early_boot_irqs_disabled);
+ /*
+ * When @wait we can deadlock when we interrupt between llist_add() and
+ * arch_send_call_function_ipi*(); when !@wait we can deadlock due to
+ * csd_lock() on because the interrupt context uses the same csd
+ * storage.
+ */
+ WARN_ON_ONCE(!in_task());
+
/* Try to fastpath. So, what's a CPU they want? Ignoring this one. */
cpu = cpumask_first_and(mask, cpu_online_mask);
if (cpu == this_cpu)