[PATCH] D20913: [asan] add primitives that allow coroutine implementations

[Philippe Daouadi via llvm-commits]

blastrock added a comment.

In http://reviews.llvm.org/D20913#448009, @dvyukov wrote:

> I see that folly always uses main thread stack as scheduler stack: always switches main->fiber/fiber->main, but not fiber1->fiber2. Some programs avoid the excessive switch by doing fiber1->fiber2. We need to make sure that we support that pattern as well.


I think this is easy to support, we can remove the warning about entering a fiber twice, then, for example, you could go main -> enter_fiber -> fiber 1 -> enter_fiber -> fiber 2 -> exit_fiber -> main.

> I wonder if it can interfere with signals (without altstack). Namely, a signal arrives when asan has setup fiber stack, but the actual switch did not happen (SP is still pointing to the old stack). Then signal handler executes something that causes __asan_handle_no_return. Seems that we can get the same crash. Need tests.


I didn't think about that. I think you are right, it will cause the warning in __asan_handle_no_return and the false positives afterwards. However, I don't know how we could avoid that... The user doing the annotation could take care of that by deferring signals between the enter_fiber and the switch to the new stack. Do you have any other idea?


http://reviews.llvm.org/D20913