mirrors/SDL
1
0
Fork 0
mirror of https://github.com/libsdl-org/SDL.git synced 2025-09-05 19:08:12 +00:00
Code Issues Packages Projects Releases Wiki Activity

audio: Never lock a device while holding the device_list_lock.

Browse Source 
Fixes various not-necessarily-corner cases ending in deadlock.
This commit is contained in:
Ryan C. Gordon
2023-10-13 14:14:56 -04:00
parent 9aeabb0b05
commit 95a9271dbf
1 changed files with 31 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
src/audio/SDL_audio.c
View File

@@ -453,15 +453,16 @@ void SDL_AudioDeviceDisconnected(SDL_AudioDevice *device)
DisconnectLogicalAudioDevice(logdev);
}
}
SDL_UnlockMutex(device->lock); // make sure nothing else is messing with the device before continuing.
SDL_UnlockMutex(device->lock);
return; // done for now. Come back when a new default device is chosen!
}
SDL_bool was_live = SDL_FALSE;
SDL_LockMutex(device->lock); // make sure nothing else is messing with the device before continuing.
// take it out of the device list.
SDL_LockRWLockForWriting(current_audio.device_list_lock);
SDL_LockMutex(device->lock); // make sure nothing else is messing with the device before continuing.
if (device == current_audio.output_devices) {
SDL_assert(device->prev == NULL);
current_audio.output_devices = device->next;
@@ -487,10 +488,12 @@ void SDL_AudioDeviceDisconnected(SDL_AudioDevice *device)
SDL_AtomicAdd(device->iscapture ? &current_audio.capture_device_count : &current_audio.output_device_count, -1);
}
// Mark device as condemned now that it's not in the device list.
SDL_AtomicSet(&device->condemned, 1);
SDL_UnlockRWLock(current_audio.device_list_lock);
// now device is not in the list, and we own it, so no one should be able to find it again, except the audio thread, which holds a pointer!
SDL_AtomicSet(&device->condemned, 1);
SDL_AtomicSet(&device->shutdown, 1); // tell audio thread to terminate.
// disconnect each attached logical device, so apps won't find their streams still bound if they get the REMOVED event before the device thread cleans up.
@@ -1115,8 +1118,29 @@ static SDL_LogicalAudioDevice *ObtainLogicalAudioDevice(SDL_AudioDeviceID devid)
const SDL_bool iscapture = (devid & (1<<0)) ? SDL_FALSE : SDL_TRUE;
SDL_LockRWLockForReading(current_audio.device_list_lock);
SDL_bool isstack = SDL_FALSE;
const int num_devices = SDL_AtomicGet(iscapture ? &current_audio.capture_device_count : &current_audio.output_device_count);
SDL_AudioDevice **devices = NULL;
for (SDL_AudioDevice *device = iscapture ? current_audio.capture_devices : current_audio.output_devices; device != NULL; device = device->next) {
if (num_devices) {
devices = SDL_small_alloc(SDL_AudioDevice *, num_devices, &isstack);
if (!devices) {
SDL_UnlockRWLock(current_audio.device_list_lock);
SDL_OutOfMemory();
return NULL;
} else {
int i = 0;
for (SDL_AudioDevice *device = iscapture ? current_audio.capture_devices : current_audio.output_devices; device != NULL; device = device->next) {
SDL_assert(i < num_devices);
devices[i++] = device;
}
SDL_assert(i == num_devices);
}
}
SDL_UnlockRWLock(current_audio.device_list_lock);
for (int i = 0; i < num_devices; i++) {
SDL_AudioDevice *device = devices[i];
SDL_LockMutex(device->lock); // caller must unlock if we choose a logical device from this guy.
SDL_assert(!SDL_AtomicGet(&device->condemned)); // shouldn't be in the list if pending deletion.
for (logdev = device->logical_devices; logdev != NULL; logdev = logdev->next) {
@@ -1130,7 +1154,7 @@ static SDL_LogicalAudioDevice *ObtainLogicalAudioDevice(SDL_AudioDeviceID devid)
SDL_UnlockMutex(device->lock); // give up this lock and try the next physical device.
}
SDL_UnlockRWLock(current_audio.device_list_lock);
SDL_small_free(devices, isstack);
}
if (!logdev) {
@@ -1167,7 +1191,6 @@ static SDL_AudioDevice *ObtainPhysicalAudioDevice(SDL_AudioDeviceID devid)
for (dev = iscapture ? current_audio.capture_devices : current_audio.output_devices; dev != NULL; dev = dev->next) {
if (dev->instance_id == devid) { // found it?
SDL_LockMutex(dev->lock); // caller must unlock.
SDL_assert(!SDL_AtomicGet(&dev->condemned)); // shouldn't be in the list if pending deletion.
break;
}
@@ -1177,6 +1200,8 @@ static SDL_AudioDevice *ObtainPhysicalAudioDevice(SDL_AudioDeviceID devid)
if (!dev) {
SDL_SetError("Invalid audio device instance ID");
} else {
SDL_LockMutex(dev->lock); // caller must unlock.
}
return dev;