Fix signal handling and add atomic operations for thread safety#800
Merged
Youw merged 1 commit intoread-interruptfrom May 5, 2026
Merged
Fix signal handling and add atomic operations for thread safety#800Youw merged 1 commit intoread-interruptfrom
Youw merged 1 commit intoread-interruptfrom
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- windows/hid.c: fix typos in hid_is_read_interrupted comment. - linux/hid.c: skip close() in hid_close() when device_handle < 0 to avoid clobbering errno on the open-failure path. - linux/hid.c: preserve eventfd() errno across free() in new_hid_device(); report the real errno from hid_open_path() instead of overwriting with ENOMEM. - linux/hid.c, netbsd/hid.c: replace `volatile int interrupted` with __atomic_load_n/__atomic_store_n (acquire/release) so the cross-thread guarantee actually holds. The pipe/eventfd handles the wakeup; the atomic covers hid_is_read_interrupted and the early-out check. - hid_read_test/main.cpp: signal handler no longer calls hid_read_interrupt() (not async-signal-safe on libusb/mac). Handler now sets an atomic flag; main thread, woken by EINTR from cin.get(), calls hid_read_interrupt(). Use sigaction without SA_RESTART on POSIX. - hid_read_test/CMakeLists.txt: lower cmake_minimum_required to 3.1.3 to match the rest of the repo; switch from target_compile_features(cxx_std_11) (CMake 3.8+) to set_target_properties(CXX_STANDARD 11) (CMake 3.1+). https://claude.ai/code/session_01JB9WGTp5xipxBFMgcJa8XT
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Summary
This PR improves thread safety and signal handling across the HIDAPI library by replacing volatile variables with proper atomic operations and refactoring signal handling to be async-signal-safe.
Key Changes
Signal Handling Improvements
hid_read_interrupt()calls in signal handler with atomic flag settingsigaction()on non-Windows platforms withoutSA_RESTARTto allowcin.get()to return on signalstd::signal()for Windows compatibilityAtomic Operations
volatile int interruptedwith proper atomic operations:dev->interrupted = 1to__atomic_store_n(&dev->interrupted, 1, __ATOMIC_RELEASE)if (dev->interrupted)toif (__atomic_load_n(&dev->interrupted, __ATOMIC_ACQUIRE))__atomic_load_n(&dev->interrupted, __ATOMIC_ACQUIRE)Bug Fixes
new_hid_device()by saving errno beforefree()callhid_open_path()to preserve and report the actual error fromnew_hid_device()hid_close()to only close device_handle if it's valid (>= 0)Build System
target_compile_features()withset_target_properties()for more explicit C++ standard configuration (CXX_STANDARD, CXX_STANDARD_REQUIRED, CXX_EXTENSIONS)Implementation Details
The atomic operations use acquire/release semantics to ensure proper synchronization between the signal handler thread and the main reading thread without requiring full sequential consistency, which improves performance while maintaining correctness.
https://claude.ai/code/session_01JB9WGTp5xipxBFMgcJa8XT