================
@@ -501,6 +501,7 @@ class PreambleThread {
}
{
+ std::unique_lock<std::mutex> Lock(Mutex);
WithContext Guard(std::move(CurrentReq->Ctx));
----------------
tahonermann wrote:
Unfortunately, I don't think this solves the issue by itself. Just prior to
exiting the above block, we are assured that `CurrentReq` has been assigned and
thus holds an object. At this point, the lock on `Mutex` has been released
which means it is possible that some other thread executing this same function
might acquire the lock on `Mutex` and reset `CurrentReq` at line 517/518 below
before this code is reached. The possibility still exists then that
`CurrentReq` doesn't hold an object at this point (or holds a partially
constructed/destructed object; note that `std::optional` doesn't promise atomic
operations).
I'm not sure what the right fix is for this issue at this point. I think it
*might* be to move `*NextReq` above into a local `Request` variable and change
the `CurrentReq` data member to just be a `bool` that indicates whether a
request is being processed. That would avoid any possibility of concurrent
modification of the `Request` object while still preserving the ability to
check if a request is being processed in `blockUntilIdle()`.
https://github.com/llvm/llvm-project/pull/118664
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