Deny Idle entry of CPU and CPU domain when it already has IPI pending (#444)

Deny Idle entry of CPU and CPU domain when it already has IPI pending

Author: sgaud-quic

drivers/cpuidle/cpuidle.c

@@ -222,6 +222,9 @@ noinstr int cpuidle_enter_state(struct cpuidle_device *dev,
 	bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
 	ktime_t time_start, time_end;
 
+	if (cpus_peek_for_pending_ipi(cpumask_of(dev->cpu)))
+		return -EBUSY;
+
 	instrumentation_begin();
 
 	/*

drivers/pmdomain/governor.c

@@ -404,15 +404,21 @@ static bool cpu_power_down_ok(struct dev_pm_domain *pd)
 		if ((idle_duration_ns >= (genpd->states[i].residency_ns +
 		    genpd->states[i].power_off_latency_ns)) &&
 		    (global_constraint >= (genpd->states[i].power_on_latency_ns +
-		    genpd->states[i].power_off_latency_ns))) {
-			genpd->state_idx = i;
-			genpd->gd->last_enter = now;
-			genpd->gd->reflect_residency = true;
-			return true;
-		}
+		    genpd->states[i].power_off_latency_ns)))
+			break;
+
 	} while (--i >= 0);
 
-	return false;
+	if (i < 0)
+		return false;
+
+	if (cpus_peek_for_pending_ipi(genpd->cpus))
+		return false;
+
+	genpd->state_idx = i;
+	genpd->gd->last_enter = now;
+	genpd->gd->reflect_residency = true;
+	return true;
 }
 
 struct dev_power_governor pm_domain_cpu_gov = {

include/linux/smp.h

@@ -168,6 +168,7 @@ int smp_call_function_any(const struct cpumask *mask,
 
 void kick_all_cpus_sync(void);
 void wake_up_all_idle_cpus(void);
+bool cpus_peek_for_pending_ipi(const struct cpumask *mask);
 
 /*
  * Generic and arch helpers
@@ -216,6 +217,10 @@ smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
 
 static inline void kick_all_cpus_sync(void) {  }
 static inline void wake_up_all_idle_cpus(void) {  }
+static inline bool cpus_peek_for_pending_ipi(const struct cpumask *mask)
+{
+	return false;
+}
 
 #define setup_max_cpus 0
 

kernel/smp.c

@@ -1087,6 +1087,28 @@ void wake_up_all_idle_cpus(void)
 }
 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);
 
+/**
+ * cpus_peek_for_pending_ipi - Check for pending IPI for CPUs
+ * @mask: The CPU mask for the CPUs to check.
+ *
+ * This function walks through the @mask to check if there are any pending IPIs
+ * scheduled, for any of the CPUs in the @mask. It does not guarantee
+ * correctness as it only provides a racy snapshot.
+ *
+ * Returns true if there is a pending IPI scheduled and false otherwise.
+ */
+bool cpus_peek_for_pending_ipi(const struct cpumask *mask)
+{
+	unsigned int cpu;
+
+	for_each_cpu(cpu, mask) {
+		if (!llist_empty(per_cpu_ptr(&call_single_queue, cpu)))
+			return true;
+	}
+
+	return false;
+}
+
 /**
  * struct smp_call_on_cpu_struct - Call a function on a specific CPU
  * @work: &work_struct