2 files changed, 15 insertions, 0 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index a517da996aaf..bfe82b63875f 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -365,6 +365,18 @@ static void cpufreq_notify_post_transition(struct cpufreq_policy *policy,
 void cpufreq_freq_transition_begin(struct cpufreq_policy *policy,
                 struct cpufreq_freqs *freqs)
 {
+
+        /*
+         * Catch double invocations of _begin() which lead to self-deadlock.
+         * ASYNC_NOTIFICATION drivers are left out because the cpufreq core
+         * doesn't invoke _begin() on their behalf, and hence the chances of
+         * double invocations are very low. Moreover, there are scenarios
+         * where these checks can emit false-positive warnings in these
+         * drivers; so we avoid that by skipping them altogether.
+         */
+        WARN_ON(!(cpufreq_driver->flags & CPUFREQ_ASYNC_NOTIFICATION)
+                                && current == policy->transition_task);
+
 wait:
         wait_event(policy->transition_wait, !policy->transition_ongoing);
 
@@ -376,6 +388,7 @@ wait:
         }
 
         policy->transition_ongoing = true;
+        policy->transition_task = current;
 
         spin_unlock(&policy->transition_lock);
 
@@ -392,6 +405,7 @@ void cpufreq_freq_transition_end(struct cpufreq_policy *policy,
         cpufreq_notify_post_transition(policy, freqs, transition_failed);
 
         policy->transition_ongoing = false;
+        policy->transition_task = NULL;
 
         wake_up(&policy->transition_wait);
 }
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 77a5fa191502..f3822f836e14 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -110,6 +110,7 @@ struct cpufreq_policy {
         bool                    transition_ongoing; /* Tracks transition status */
         spinlock_t              transition_lock;
         wait_queue_head_t       transition_wait;
+        struct task_struct      *transition_task; /* Task which is doing the transition */
 };
 
 /* Only for ACPI */