S32 LLQueuedThread::processNextRequest()
{
QueuedRequest *req;
// Get next request from pool
lockData();
while(1)
{
req = NULL;
if (mRequestQueue.empty())
{
break;
}
req = *mRequestQueue.begin();
mRequestQueue.erase(mRequestQueue.begin());
if ((req->getFlags() & FLAG_ABORT) || (mStatus == QUITTING))
{
req->setStatus(STATUS_ABORTED);
// Unlock, because we can't call finishRequest() while keeping this lock:
// generateHandle() takes this lock too and is called while holding a lock
// (ie LLTextureFetchWorker::mWorkMutex) that finishRequest will lock too,
// causing a dead lock.
// Although a complete rewrite of LLQueuedThread is in order because it's
// far from robust the way it handles it's locking; the following rationale
// at least makes plausible that releasing the lock here SHOULD work if
// the original coder didn't completely f**k up: if before the QueuedRequest
// req was only accessed while keeping the lock, then it still should
// never happen that another thread is waiting for this lock in order to
// access the QueuedRequest: a few lines lower we delete it.
// In other words, if directly after releasing this lock another thread
// would access req, then that can only happen by finding it again in
// either mRequestQueue or mRequestHash. We already deleted it from the
// first, so this access would have to happen by finding it in mRequestHash.
// Such access happens in the following functions:
// 1) LLQueuedThread::shutdown -- but it does that anyway, as it doesn't use any locking.
// 2) LLQueuedThread::generateHandle -- might skip our handle while before it would block until we deleted it. Skipping it is actually better.
// 3) LLQueuedThread::waitForResult -- this now doesn't touch the req when it has the flag FLAG_LOCKED set.
// 4) LLQueuedThread::getRequest -- whereever this is used, FLAG_LOCKED is tested before using the req.
// 5) LLQueuedThread::getRequestStatus -- this is a read-only operation on the status, which should never be changed from finishRequest().
// 6) LLQueuedThread::abortRequest -- it doesn't seem to hurt to add flags (if this happens at all), while calling finishRequest().
// 7) LLQueuedThread::setFlags -- same.
// 8) LLQueuedThread::setPriority -- doesn't access req with status STATUS_ABORTED, STATUS_COMPLETE or STATUS_INPROGRESS.
// 9) LLQueuedThread::completeRequest -- now sets FLAG_AUTO_COMPLETE instead of deleting the req, if FLAG_LOCKED is set, so that deletion happens here when finishRequest returns.
req->setFlags(FLAG_LOCKED);
unlockData();
req->finishRequest(false);
lockData();
req->resetFlags(FLAG_LOCKED);
if ((req->getFlags() & FLAG_AUTO_COMPLETE))
{
req->resetFlags(FLAG_AUTO_COMPLETE);
mRequestHash.erase(req);
// check();
unlockData();
req->deleteRequest();
lockData();
}
continue;
}
llassert_always(req->getStatus() == STATUS_QUEUED);
break;
}
U32 start_priority = 0 ;
if (req)
{
req->setStatus(STATUS_INPROGRESS);
start_priority = req->getPriority();
}
unlockData();
// This is the only place we will call req->setStatus() after
// it has initially been seet to STATUS_QUEUED, so it is
// safe to access req.
if (req)
{
// process request
bool complete = req->processRequest();
if (complete)
{
lockData();
req->setStatus(STATUS_COMPLETE);
req->setFlags(FLAG_LOCKED);
unlockData();
req->finishRequest(true);
if ((req->getFlags() & FLAG_AUTO_COMPLETE))
{
lockData();
req->resetFlags(FLAG_AUTO_COMPLETE);
mRequestHash.erase(req);
// check();
req->resetFlags(FLAG_LOCKED);
unlockData();
req->deleteRequest();
}
else
{
req->resetFlags(FLAG_LOCKED);
}
}
else
{
lockData();
req->setStatus(STATUS_QUEUED);
mRequestQueue.insert(req);
unlockData();
if (mThreaded && start_priority < PRIORITY_NORMAL)
{
ms_sleep(1); // sleep the thread a little
}
}
}
S32 pending = getPending();
return pending;
}
