glibc v2.30 added the pthread_mutex_clocklock, pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock functions. These accept CLOCK_MONOTONIC, so they can be used to implement proper steady_clock support in timed_mutex, recursive_timed_mutex and shared_timed_mutex that is immune to the system clock being warped.
Unfortunately we can't warp the system clock in the testsuite, so it's not possible to automatically ensure that the system_clock test cases result in a wait on CLOCK_REALTIME and steady_clock test cases result in a wait on CLOCK_MONOTONIC. It's recommended to run the test under strace(1) and check whether the expected futex calls are made by glibc or ltrace(1) and check whether the expected pthread calls are made. The easiest way to do this is to copy and paste the line used to build the test from the output of running the tests (for example): make check-target-libstdc++-v3 RUNTESTFLAGS="conformance.exp=30_threads/shared_mutex/* -v -v" to compile the test with only the tests for one clock enabled and then run it as: strace -f ./1.exe You should see calls to: futex(..., FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, ...) with large values of tv_sec when using system_clock and calls to: futex(..., FUTEX_WAIT_BITSET_PRIVATE, ...) Alternatively, you can use: ltrace -f ./1.exe and look for calls to pthread_mutex_clocklock, pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock with a parameter of 1 for CLOCK_MONOTONIC and with values of tv_sec based on the system uptime when using steady_clock. This series also adds some extra tests and fixes some other minor problems with the existing implementation and tests. Changes since v1[1]: * Fix flaw pointed out[2] by François Dumont and add tests to prove that. [1] https://gcc.gnu.org/ml/libstdc++/2019-09/msg00106.html [2] https://gcc.gnu.org/ml/libstdc++/2019-10/msg00021.html Mike Crowe (11): libstdc++ testsuite: Check return value from timed_mutex::try_lock_until libstdc++ testsuite: Add timed_mutex::try_lock_until test libstdc++ testsuite: Also test timed_mutex with steady_clock libstdc++ testsuite: Also test unique_lock::try_lock_until with steady_clock PR libstdc++/78237 Add full steady_clock support to timed_mutex libstdc++ testsuite: Move slow_clock to its own header PR libstdc++/91906 Fix timed_mutex::try_lock_until on arbitrary clock libstdc++ testsuite: Also test shared_timed_mutex with steady_clock libstdc++ shared_mutex: Add full steady_clock support to shared_timed_mutex libstdc++ timed_mutex: Ensure that try_lock_for waits for long enough shared_mutex: Fix try_lock_until and try_lock_shared_until on arbitrary clock libstdc++-v3/acinclude.m4 | 64 +++++++++++++++++++++++++++- libstdc++-v3/config.h.in | 7 +++- libstdc++-v3/configure | 170 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- libstdc++-v3/configure.ac | 6 +++- libstdc++-v3/include/std/mutex | 60 +++++++++++++++++++++---- libstdc++-v3/include/std/shared_mutex | 117 +++++++++++++++++++++++++++++++++++++++++--------- libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc | 17 +------- libstdc++-v3/testsuite/30_threads/recursive_timed_mutex/try_lock_until/3.cc | 76 ++++++++++++++++++++++++++++++++- libstdc++-v3/testsuite/30_threads/shared_timed_mutex/try_lock/3.cc | 17 ++++--- libstdc++-v3/testsuite/30_threads/shared_timed_mutex/try_lock_until/1.cc | 87 +++++++++++++++++++++++++++++++++++++- libstdc++-v3/testsuite/30_threads/shared_timed_mutex/try_lock_until/2.cc | 75 ++++++++++++++++++++++++++++++++- libstdc++-v3/testsuite/30_threads/timed_mutex/try_lock_until/3.cc | 76 ++++++++++++++++++++++++++++++++- libstdc++-v3/testsuite/30_threads/timed_mutex/try_lock_until/4.cc | 68 +++++++++++++++++++++++++++++- libstdc++-v3/testsuite/30_threads/timed_mutex/try_lock_until/57641.cc | 18 +++++--- libstdc++-v3/testsuite/30_threads/unique_lock/locking/4.cc | 14 ++++-- libstdc++-v3/testsuite/util/slow_clock.h | 38 ++++++++++++++++- 16 files changed, 850 insertions(+), 60 deletions(-) create mode 100644 libstdc++-v3/testsuite/30_threads/recursive_timed_mutex/try_lock_until/3.cc create mode 100644 libstdc++-v3/testsuite/30_threads/shared_timed_mutex/try_lock_until/1.cc create mode 100644 libstdc++-v3/testsuite/30_threads/shared_timed_mutex/try_lock_until/2.cc create mode 100644 libstdc++-v3/testsuite/30_threads/timed_mutex/try_lock_until/3.cc create mode 100644 libstdc++-v3/testsuite/30_threads/timed_mutex/try_lock_until/4.cc create mode 100644 libstdc++-v3/testsuite/util/slow_clock.h base-commit: 32244cd831c781020ebc44d7b557149d9d26c6f5 -- git-series 0.9.1
