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Code Issues Releases Activity

LP-155 Workaround failing callback deregistration

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Deregistration of hid_device_removal_callback fails because the call to
IOHIDDeviceRegisterRemovalCallback doesn't deregister it as it should.

This causes crashes when hid_device_removal_callback is called after
the read_thread has been shutdown.

This patch works around this problem by:

1) Letting the 'dev' hid_device, so that the callback can safely
   read the struct, even after the read_thread has been shut down
   and the memory should have been freed.

2) Making sure that the two racing callbacks that previously
   called CFRunLoopStop, hid_device_removal_callback and
   perform_signal_callback, now synchronize and make sure
    that CFRunLoopStop is only called once.
This commit is contained in:
Stefan Karlsson 2015-10-15 21:12:11 +02:00
parent 295562694b
commit 6504ce448e
1 changed files with 46 additions and 3 deletions
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49
ground/gcs/src/plugins/ophid/hidapi/mac/hid.c
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@ -118,6 +118,8 @@ struct hid_device_ {
pthread_barrier_t barrier; /* Ensures correct startup sequence */
pthread_barrier_t shutdown_barrier; /* Ensures correct shutdown sequence */
int shutdown_thread;
bool run_loop_stopped;
};
static hid_device *new_hid_device(void)
@ -133,6 +135,7 @@ static hid_device *new_hid_device(void)
dev->input_report_buf = NULL;
dev->input_reports = NULL;
dev->shutdown_thread = 0;
dev->run_loop_stopped = 0;
/* Thread objects */
pthread_mutex_init(&dev->mutex, NULL);
@ -173,7 +176,13 @@ static void free_hid_device(hid_device *dev)
pthread_mutex_destroy(&dev->mutex);
/* Free the structure itself. */
free(dev);
// Note: We can't delete the dev struct, since we might get
// an asynchronous call to hid_device_removal_callback, which
// gets the dev passed as an argument.
//
// See stop_run_loop for an explanation why this happens.
//
// free(dev);
}
static IOHIDManagerRef hid_mgr = 0x0;
@ -548,6 +557,38 @@ hid_device * HID_API_EXPORT hid_open(unsigned short vendor_id, unsigned short pr
return handle;
}
// Use a shared mutex for all devices.
static pthread_mutex_t stop_run_loop_mutex = PTHREAD_MUTEX_INITIALIZER;
static void stop_run_loop(hid_device* dev)
{
bool stop_run_loop;
// There seems to be a bug in IOHIDDeviceRegisterRemovalCallback,
// which causes de-registration of the removal callback
// (hid_device_removal_callbacl) to fail.
//
// Because of this, hid_device_removal_callback will be called after
// the read_thread has executed perform_signal_callback, which also
// calls CFRunLoopStop. This second call to CFRunLoopStop is executed
// in another thread, sometimes after the read_thread has executed, and
// this causes crashes.
//
// Because of this asynchronous call to hid_device_removal_callback,
// the dev structs are leaked, for now.
pthread_mutex_lock(&stop_run_loop_mutex);
stop_run_loop = !dev->run_loop_stopped;
if (stop_run_loop) {
dev->run_loop_stopped = 1;
}
pthread_mutex_unlock(&stop_run_loop_mutex);
if (stop_run_loop) {
CFRunLoopStop(dev->run_loop);
}
}
static void hid_device_removal_callback(void *context, IOReturn result,
void *sender)
{
@ -555,7 +596,8 @@ static void hid_device_removal_callback(void *context, IOReturn result,
hid_device *d = context;
d->disconnected = 1;
CFRunLoopStop(d->run_loop);
stop_run_loop(d);
}
/* The Run Loop calls this function for each input report received.
@ -614,7 +656,8 @@ static void hid_report_callback(void *context, IOReturn result, void *sender,
static void perform_signal_callback(void *context)
{
hid_device *dev = context;
CFRunLoopStop(dev->run_loop); /*TODO: CFRunLoopGetCurrent()*/
stop_run_loop(dev);
}
static void *read_thread(void *param)