Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Implement std::condition_variable via pthread_cond_clockwait() where …
…available std::condition_variable is currently implemented via pthread_cond_timedwait() on systems that use pthread. This is problematic, since that function waits by default on CLOCK_REALTIME and libc++ does not provide any mechanism to change from this default. Due to this, regardless of if condition_variable::wait_until() is called with a chrono::system_clock or chrono::steady_clock parameter, condition_variable::wait_until() will wait using CLOCK_REALTIME. This is not accurate to the C++ standard as calling condition_variable::wait_until() with a chrono::steady_clock parameter should use CLOCK_MONOTONIC. This is particularly problematic because CLOCK_REALTIME is a bad choice as it is subject to discontinuous time adjustments, that may cause condition_variable::wait_until() to immediately timeout or wait indefinitely. This change fixes this issue with a new POSIX function, pthread_cond_clockwait() proposed on http://austingroupbugs.net/view.php?id=1216. The new function is similar to pthread_cond_timedwait() with the addition of a clock parameter that allows it to wait using either CLOCK_REALTIME or CLOCK_MONOTONIC, thus allowing condition_variable::wait_until() to wait using CLOCK_REALTIME for chrono::system_clock and CLOCK_MONOTONIC for chrono::steady_clock. pthread_cond_clockwait() is implemented in glibc (2.30 and later) and Android's bionic (Android API version 30 and later). This change additionally makes wait_for() and wait_until() with clocks other than chrono::system_clock use CLOCK_MONOTONIC.<Paste> llvm-svn: 372016
- Loading branch information
Showing
3 changed files
with
156 additions
and
28 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters