TSan recently got the "ignore_noninstrumented_modules" flag, which disables tracking of read and writes that come from noninstrumented modules (via interceptors). This is a way of suppressing false positives coming from system libraries and other noninstrumented code. This patch turns this on by default on Darwin, where it's supposed to replace the previous solution, "ignore_interceptors_accesses", which disables tracking in *all* interceptors. The new approach should re-enable TSan's ability to find races via interceptors on Darwin.
Differential Revision: https://reviews.llvm.org/D29041
llvm-svn: 292981
GCD (libdispatch) has a concept of “target queues”: Each queue has either an implicit or explicit target queue, where the task is handed over to when it’s time to execute it. For example, a concurrent queue can have a serial target queue (effectively making the first queue serial), or multiple queues can have the same serial target queue (which means tasks in all the queues are mutually excluded). Thus we need to acquire-release semantics on the full “chain” of target queues.
This patch changes the way we Acquire() and Release() when executing tasks in queues. Now we’ll walk the chain of target queues and synchronize on each queue that is serial (or when dealing with a barrier block). This should avoid false positives when using dispatch_set_target_queue().
Differential Revision: https://reviews.llvm.org/D25835
llvm-svn: 285613
Kuba Mracek