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Make ma_context/device_get_backend_state() atomic.

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It is technically possible for a backend to create a thread which
calls `ma_context/device_get_backend_state()` before miniaudio has
set the internal pointer.
This commit is contained in:
David Reid
2025-07-21 12:43:13 +10:00
parent 93167d108e
commit bd75bcb592
1 changed files with 23 additions and 20 deletions
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miniaudio.h
+23 -20
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@@ -7599,20 +7599,20 @@ struct ma_context_config
struct ma_context struct ma_context
{ {
ma_device_backend_vtable* pVTable; /* New new system. */ ma_device_backend_vtable* pVTable; /* New new system. */
void* pBackendState; /* Backend state created by the backend. This will be passed to the relevant backend functions. */ MA_ATOMIC(MA_SIZEOF_PTR, void*) pBackendState; /* Backend state created by the backend. This will be passed to the relevant backend functions. */
ma_log* pLog; ma_log* pLog;
ma_log log; /* Only used if the log is owned by the context. The pLog member will be set to &log in this case. */ ma_log log; /* Only used if the log is owned by the context. The pLog member will be set to &log in this case. */
ma_thread_priority threadPriority; ma_thread_priority threadPriority;
size_t threadStackSize; size_t threadStackSize;
void* pUserData; void* pUserData;
ma_allocation_callbacks allocationCallbacks; ma_allocation_callbacks allocationCallbacks;
ma_mutex deviceEnumLock; /* Used to make ma_context_get_devices() thread safe. */ ma_mutex deviceEnumLock; /* Used to make ma_context_get_devices() thread safe. */
ma_mutex deviceInfoLock; /* Used to make ma_context_get_device_info() thread safe. */ ma_mutex deviceInfoLock; /* Used to make ma_context_get_device_info() thread safe. */
ma_uint32 deviceInfoCapacity; /* Total capacity of pDeviceInfos. */ ma_uint32 deviceInfoCapacity; /* Total capacity of pDeviceInfos. */
ma_uint32 playbackDeviceInfoCount; ma_uint32 playbackDeviceInfoCount;
ma_uint32 captureDeviceInfoCount; ma_uint32 captureDeviceInfoCount;
ma_device_info* pDeviceInfos; /* Playback devices first, then capture. */ ma_device_info* pDeviceInfos; /* Playback devices first, then capture. */
#if defined(MA_WIN32) #if defined(MA_WIN32)
struct struct
@@ -7645,24 +7645,24 @@ struct ma_device
ma_context* pContext; ma_context* pContext;
ma_device_type type; ma_device_type type;
ma_uint32 sampleRate; ma_uint32 sampleRate;
ma_atomic_device_status state; /* The state of the device is variable and can change at any time on any thread. Must be used atomically. */ ma_atomic_device_status state; /* The state of the device is variable and can change at any time on any thread. Must be used atomically. */
ma_device_data_proc onData; /* Set once at initialization time and should not be changed after. */ ma_device_data_proc onData; /* Set once at initialization time and should not be changed after. */
ma_device_notification_proc onNotification; /* Set once at initialization time and should not be changed after. */ ma_device_notification_proc onNotification; /* Set once at initialization time and should not be changed after. */
void* pUserData; /* Application defined data. */ void* pUserData; /* Application defined data. */
void* pBackendState; /* Backend state created by the backend. This will be passed to the relevant backend functions. */ MA_ATOMIC(MA_SIZEOF_PTR, void*) pBackendState; /* Backend state created by the backend. This will be passed to the relevant backend functions. */
ma_mutex startStopLock; ma_mutex startStopLock;
ma_event wakeupEvent; ma_event wakeupEvent;
ma_event startEvent; ma_event startEvent;
ma_event stopEvent; ma_event stopEvent;
ma_thread thread; ma_thread thread;
ma_result workResult; /* This is set by the worker thread after it's finished doing a job. */ ma_result workResult; /* This is set by the worker thread after it's finished doing a job. */
ma_bool8 isOwnerOfContext; /* When set to true, uninitializing the device will also uninitialize the context. Set to true when NULL is passed into ma_device_init(). */ ma_bool8 isOwnerOfContext; /* When set to true, uninitializing the device will also uninitialize the context. Set to true when NULL is passed into ma_device_init(). */
ma_bool8 noPreSilencedOutputBuffer; ma_bool8 noPreSilencedOutputBuffer;
ma_bool8 noClip; ma_bool8 noClip;
ma_bool8 noDisableDenormals; ma_bool8 noDisableDenormals;
ma_bool8 noFixedSizedCallback; ma_bool8 noFixedSizedCallback;
ma_atomic_float masterVolumeFactor; /* Linear 0..1. Can be read and written simultaneously by different threads. Must be used atomically. */ ma_atomic_float masterVolumeFactor; /* Linear 0..1. Can be read and written simultaneously by different threads. Must be used atomically. */
ma_duplex_rb duplexRB; /* Intermediary buffer for duplex devices on asynchronous backends. */ ma_duplex_rb duplexRB; /* Intermediary buffer for duplex devices on asynchronous backends. */
struct struct
{ {
ma_resample_algorithm algorithm; ma_resample_algorithm algorithm;
@@ -44034,7 +44034,7 @@ MA_API ma_result ma_context_init(const ma_device_backend_config* pBackends, ma_u
ma_log_postf(ma_context_get_log(pContext), MA_LOG_LEVEL_DEBUG, "Successfully initialized %s backend.", backendInfo.pName); ma_log_postf(ma_context_get_log(pContext), MA_LOG_LEVEL_DEBUG, "Successfully initialized %s backend.", backendInfo.pName);
pContext->pVTable = backend.pVTable; pContext->pVTable = backend.pVTable;
pContext->pBackendState = pContextState; ma_atomic_store_explicit_ptr((volatile void**)&pContext->pBackendState, pContextState, ma_atomic_memory_order_relaxed);
result = ma_mutex_init(&pContext->deviceEnumLock); result = ma_mutex_init(&pContext->deviceEnumLock);
if (result != MA_SUCCESS) { if (result != MA_SUCCESS) {
@@ -44122,7 +44122,7 @@ MA_API void* ma_context_get_backend_state(ma_context* pContext)
return NULL; return NULL;
} }
return pContext->pBackendState; return ma_atomic_load_explicit_ptr((volatile void**)&pContext->pBackendState, ma_atomic_memory_order_relaxed);
} }
@@ -44414,6 +44414,7 @@ MA_API ma_result ma_device_init(ma_context* pContext, const ma_device_config* pC
ma_result result; ma_result result;
ma_device_descriptor descriptorPlayback; ma_device_descriptor descriptorPlayback;
ma_device_descriptor descriptorCapture; ma_device_descriptor descriptorCapture;
void* pBackendState;
/* The context can be null, in which case we self-manage it. */ /* The context can be null, in which case we self-manage it. */
if (pContext == NULL) { if (pContext == NULL) {
@@ -44568,7 +44569,7 @@ MA_API ma_result ma_device_init(ma_context* pContext, const ma_device_config* pC
} }
result = pContext->pVTable->onDeviceInit(pDevice, ma_device_config_find_backend_config(pConfig, pContext->pVTable), &descriptorPlayback, &descriptorCapture, &pDevice->pBackendState); result = pContext->pVTable->onDeviceInit(pDevice, ma_device_config_find_backend_config(pConfig, pContext->pVTable), &descriptorPlayback, &descriptorCapture, &pBackendState);
if (result != MA_SUCCESS) { if (result != MA_SUCCESS) {
ma_event_uninit(&pDevice->startEvent); ma_event_uninit(&pDevice->startEvent);
ma_event_uninit(&pDevice->wakeupEvent); ma_event_uninit(&pDevice->wakeupEvent);
@@ -44576,6 +44577,8 @@ MA_API ma_result ma_device_init(ma_context* pContext, const ma_device_config* pC
return result; return result;
} }
ma_atomic_store_explicit_ptr((volatile void**)&pDevice->pBackendState, pBackendState, ma_atomic_memory_order_relaxed);
result = ma_device_post_init(pDevice, pConfig->deviceType, &descriptorPlayback, &descriptorCapture); result = ma_device_post_init(pDevice, pConfig->deviceType, &descriptorPlayback, &descriptorCapture);
if (result != MA_SUCCESS) { if (result != MA_SUCCESS) {
@@ -44930,7 +44933,7 @@ MA_API void* ma_device_get_backend_state(ma_device* pDevice)
return NULL; return NULL;
} }
return pDevice->pBackendState; return ma_atomic_load_explicit_ptr((volatile void**)&pDevice->pBackendState, ma_atomic_memory_order_relaxed);
} }