https://bugs.llvm.org/show_bug.cgi?id=49721
Bug ID: 49721
Summary: std::binary_semaphore::try_acquire() blocks forever
Product: libc++
Version: unspecified
Hardware: All
OS: All
Status: CONFIRMED
Severity: normal
Priority: P
Component: All Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Created attachment 24693
--> https://bugs.llvm.org/attachment.cgi?id=24693&action=edit
repro
[thread.sema.cnt] says for try_acquire():
Effects: Attempts to atomically decrement counter if it is positive, without
blocking. [...]
libc++'s try_acquire() maps to
try_acquire_for(std::chrono::nanoseconds::zero()) which in the case of
std::binary_semaphore boils down to __libcpp_thread_poll_with_backoff(), which
treats a zero timeout as an infinite timeout, resulting in try_acquire()
blocking forever if it's unable to decrement.
The attached .cpp file demonstrates the problem.
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