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f38b1f243e
- Switch the reference counting to a RCU based per-CPU reference to
address a performance bottleneck vs. the single instance rcuref
variant.
- Make the futex selftest build on 32-bit architectures which only
support 64-bit time_t, e.g. RISCV-32.
- Cleanups and improvements in selftests and futex bench
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Merge tag 'locking-futex-2025-07-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull futex updates from Thomas Gleixner:
- Switch the reference counting to a RCU based per-CPU reference to
address a performance bottleneck vs the single instance rcuref
variant
- Make the futex selftest build on 32-bit architectures which only
support 64-bit time_t, e.g. RISCV-32
- Cleanups and improvements in selftests and futex bench
* tag 'locking-futex-2025-07-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
selftests/futex: Fix spelling mistake "Succeffuly" -> "Successfully"
selftests/futex: Define SYS_futex on 32-bit architectures with 64-bit time_t
perf bench futex: Remove support for IMMUTABLE
selftests/futex: Remove support for IMMUTABLE
futex: Remove support for IMMUTABLE
futex: Make futex_private_hash_get() static
futex: Use RCU-based per-CPU reference counting instead of rcuref_t
selftests/futex: Adapt the private hash test to RCU related changes
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| run.sh | ||
Futex Test ========== Futex Test is intended to thoroughly test the Linux kernel futex system call API. Functional tests shall test the documented behavior of the futex operation code under test. This includes checking for proper behavior under normal use, odd corner cases, regression tests, and abject abuse and misuse. Futextest will also provide example implementation of mutual exclusion primitives. These can be used as is in user applications or can serve as examples for system libraries. These will likely be added to either a new lib/ directory or purely as header files under include/, I'm leaning toward the latter. Quick Start ----------- # make # ./run.sh Design and Implementation Goals ------------------------------- o Tests should be as self contained as is practical so as to facilitate sharing the individual tests on mailing list discussions and bug reports. o The build system shall remain as simple as possible, avoiding any archive or shared object building and linking. o Where possible, any helper functions or other package-wide code shall be implemented in header files, avoiding the need to compile intermediate object files. o External dependencies shall remain as minimal as possible. Currently gcc and glibc are the only dependencies. o Tests return 0 for success and < 0 for failure. Output Formatting ----------------- Test output shall be easily parsable by both human and machine. Title and results are printed to stdout, while intermediate ERROR or FAIL messages are sent to stderr. Tests shall support the -c option to print PASS, FAIL, and ERROR strings in color for easy visual parsing. Output shall conform to the following format: test_name: Description of the test Arguments: arg1=val1 #units specified for clarity where appropriate ERROR: Description of unexpected error FAIL: Reason for test failure # FIXME: Perhaps an " INFO: informational message" option would be # useful here. Using -v to toggle it them on and off, as with -c. # there may be multiple ERROR or FAIL messages Result: (PASS|FAIL|ERROR) Naming ------ o FIXME: decide on a sane test naming scheme. Currently the tests are named based on the primary futex operation they test. Eventually this will become a problem as we intend to write multiple tests which collide in this namespace. Perhaps something like "wait-wake-1" "wait-wake-2" is adequate, leaving the detailed description in the test source and the output. Coding Style ------------ o The Futex Test project adheres to the coding standards set forth by Linux kernel as defined in the Linux source Documentation/process/coding-style.rst.