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Commit f33edb2c authored by Martin Brabham's avatar Martin Brabham
Browse files

DO NOT MERGE: osi: Offload mutex pointer to local scope 

Create a shared_ptr for the callback_mutex in the alarm struct.
When performing the callback, make a local shared_ptr reference.
lock_guard on the local shared_ptr reference.

Bug: 117997080
Test: atest net_test_bluetooth
Change-Id: Iab800f720f4ccc4735e4d494e0d458eb97b40a4a
parent 54ec3c1a

system/osi/src/alarm.cc

+12 −5
Original line number Diff line number Diff line
@@ -91,7 +91,7 @@ struct alarm_t { 
  // potentially long-running callback is executing. |alarm_cancel| uses this

  // mutex to provide a guarantee to its caller that the callback will not be

  // in progress when it returns.

  std::recursive_mutex* callback_mutex;

  std::shared_ptr<std::recursive_mutex> callback_mutex;

  uint64_t creation_time_ms;

  uint64_t period_ms;

  uint64_t deadline_ms;
@@ -174,7 +174,8 @@ static alarm_t* alarm_new_internal(const char* name, bool is_periodic) { 


  alarm_t* ret = static_cast<alarm_t*>(osi_calloc(sizeof(alarm_t)));



  ret->callback_mutex = new std::recursive_mutex;

  std::shared_ptr<std::recursive_mutex> ptr(new std::recursive_mutex());

  ret->callback_mutex = ptr;

  ret->is_periodic = is_periodic;

  ret->stats.name = osi_strdup(name);
@@ -191,7 +192,7 @@ void alarm_free(alarm_t* alarm) { 
  if (!alarm) return;



  alarm_cancel(alarm);

  delete alarm->callback_mutex;



  osi_free((void*)alarm->stats.name);

  alarm->closure.~CancelableClosureInStruct();

  osi_free(alarm);
@@ -245,13 +246,15 @@ void alarm_cancel(alarm_t* alarm) { 
  CHECK(alarms != NULL);

  if (!alarm) return;



  std::shared_ptr<std::recursive_mutex> local_mutex_ref;

  {

    std::lock_guard<std::mutex> lock(alarms_mutex);

    local_mutex_ref = alarm->callback_mutex;

    alarm_cancel_internal(alarm);

  }



  // If the callback for |alarm| is in progress, wait here until it completes.

  std::lock_guard<std::recursive_mutex> lock(*alarm->callback_mutex);

  std::lock_guard<std::recursive_mutex> lock(*local_mutex_ref);

}



// Internal implementation of canceling an alarm.
@@ -265,6 +268,7 @@ static void alarm_cancel_internal(alarm_t* alarm) { 
  alarm->deadline_ms = 0;

  alarm->prev_deadline_ms = 0;

  alarm->callback = NULL;

  alarm->callback_mutex.reset();

  alarm->data = NULL;

  alarm->stats.canceled_count++;

  alarm->queue = NULL;
@@ -583,7 +587,10 @@ static void alarm_ready_generic(alarm_t* alarm, 
    alarm->queue = NULL;

  }



  std::lock_guard<std::recursive_mutex> cb_lock(*alarm->callback_mutex);

  // Increment the reference count of the mutex so it doesn't get freed

  // before the callback gets finished executing.

  std::shared_ptr<std::recursive_mutex> local_mutex_ref = alarm->callback_mutex;

  std::lock_guard<std::recursive_mutex> cb_lock(*local_mutex_ref);

  lock.unlock();



  // Update the statistics

system/osi/test/alarm_test.cc

+14 −0
Original line number Diff line number Diff line
@@ -344,3 +344,17 @@ TEST_F(AlarmTest, test_callback_free_race) { 
  }

  alarm_cleanup();

}



static void remove_cb(void* data) {

  alarm_free((alarm_t*)data);

  semaphore_post(semaphore);

}



TEST_F(AlarmTest, test_delete_during_callback) {

  for (int i = 0; i < 1000; ++i) {

    alarm_t* alarm = alarm_new("alarm_test.test_delete_during_callback");

    alarm_set(alarm, 0, remove_cb, alarm);

    semaphore_wait(semaphore);

  }

  alarm_cleanup();

}