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

1 files changed, 16 insertions, 0 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
index 616d4d114847..7dbcb402c2fc 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)