Updated: April 19, 2023 |
Atomically set a flag (C11)
#include <stdatomic.h> _Bool atomic_flag_test_and_set( volatile atomic_flag *obj ); _Bool atomic_flag_test_and_set_explicit( volatile atomic_flag *obj, memory_order order );
The atomic_flag_test_and_set() and atomic_flag_test_and_set_explicit() functions atomically set the given atomic flag to true and return the previous value. The atomic_flag_test_and_set() function orders memory access according to memory_order_seq_cst; atomic_flag_test_and_set_explicit() orders them as specified by order.
The implementation of atomic functions may depend on the architecture. For more information, see LL/SC vs LSE atomic operations in the description in Building Embedded Systems of the cpuinfo area of the system page.
The previous value.
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | Read the Caveats |
Signal handler | Read the Caveats |
Thread | Yes |
If this function is lock-free (see atomic_is_lock_free()), it's safe to call it from an ISR or signal handler.