Sorry, by map/unmap, I meant lock/unlock. All D3D9 calls must occur on your main thread. The worker can generate data in between a call to lock and unlock.
e.g.

D3DLOCKED_RECT result = {};
texture->LockRect(0, &result, NULL, D3DLOCK_DISCARD);
SignalWorkerThreadToGenerateData( result );
... later ...
if( WorkerThreadIsDone() )
	texture->UnlockRect(0);


void* result = 0;
buffer->Lock(0, 0, &result, 0);
SignalWorkerThreadToGenerateData( result );
... later ...
if( WorkerThreadIsDone() )
	buffer->Unlock();

Sorry, by map/unmap, I meant lock/unlock. All D3D9 calls must occur on your main thread. The worker can generate data in between a call to lock and unlock.
e.g.

D3DLOCKED_RECT result = {};
texture->LockRect(0, &result, NULL, D3DLOCK_DISCARD);
SignalWorkerThreadToGenerateData( result );
... later ...
if( WorkerThreadIsDone() )
	texture->UnlockRect(0);


void* result = 0;
buffer->Lock(0, 0, &result, 0);
SignalWorkerThreadToGenerateData( result );
... later ...
if( WorkerThreadIsDone() )
	buffer->Unlock();

Sorry, by map/unmap, I meant lock/unlock. All D3D9 calls must occur on your main thread. The worker can generate data in between a call to lock and unlock.
e.g.

D3DLOCKED_RECT result = {};
texture->LockRect(0, &result, NULL, D3DLOCK_DISCARD);
SignalWorkerThreadToGenerateData( result );
... later ...
if( WorkerThreadIsDone() )
	texture->UnlockRect(0);


void* result = 0;
buffer->Lock(0, 0, &lockedData, 0);
SignalWorkerThreadToGenerateData( result );
... later ...
if( WorkerThreadIsDone() )
	buffer->Unlock();