Clear a bit and return its old value
int __test_and_clear_bit(long nr, volatile unsigned long * addr);
nr
Bit to clear
addr
Address to count from
This operation is non-atomic and can be reordered. If two examples of this operation race, one can appear to succeed but actually fail. You must protect multiple accesses with a lock.
the operation is performed atomically with respect to the local CPU, but not other CPUs. Portable code should not rely on this behaviour. KVM relies on this behaviour on x86 for modifying memory that is also
don't change this without also updating arch/x86/kernel/kvm.c