in most of the atomic operations. Now for these operations, you can
use the normal atomic operation, you can use the operation with a read
barrier, or you can use the operation with a write barrier. The function
names follow the same semantics used in the ia64 instruction set. An
atomic operation with a read barrier has the extra suffix 'acq', due to
it having "acquire" semantics. An atomic operation with a write barrier
has the extra suffix 'rel'. These suffixes are inserted between the
name of the operation to perform and the typename. For example, the
atomic_add_int() function now has 3 variants:
- atomic_add_int() - this is the same as the previous function
- atomic_add_acq_int() - this function combines the add operation with a
read memory barrier
- atomic_add_rel_int() - this function combines the add operation with a
write memory barrier
- Add 'ptr' to the list of types that we can perform atomic operations
on. This allows one to do atomic operations on uintptr_t's. This is
useful in the mutex code, for example, because the actual mutex lock is
a pointer.
- Add two new operations for doing loads and stores with memory barriers.
The new load operations use a read barrier before the load, and the
new store operations use a write barrier after the load. For example,
atomic_load_acq_int() will atomically load an integer as well as
enforcing a read barrier.
fixes a serious problem with the previous version where an input could
have been placed in the same register as an output which would stop
the inline from working properly.
* Redo atomic_{set,clear,add,subtract}_{32,64} as inlines since the code
sequence is shorter than the call sequence to the code in atomic.s.
I will remove the functions from atomic.s after a grace period to allow
people to rebuild kernel modules.
Add some overflow checks to read/write (from bde).
Change all modifications to vm_page::flags, vm_page::busy, vm_object::flags
and vm_object::paging_in_progress to use operations which are not
interruptable.
Reviewed by: Bruce Evans <bde@zeta.org.au>
