On 10/28/22 01:59, Alex Bennée wrote:
I'm unwilling to put an expensive test like a function call
(have_mmap_lock) before an inexpensive test like pointer != NULL.
Is it really that more expensive?
Well, yes. I mean, the function call isn't really slow, but it isn't single-cycle like a
comparison against 0.
Sure, I guess I'm just trying to avoid having so many returns out of
the code at various levels of nesting. The page_get_target_data code is
harder to follow. What about:
int page_get_flags(target_ulong address)
{
PageFlagsNode *p = pageflags_find(address, address);
/*
* See util/interval-tree.c re lockless lookups: no false positives but
* there are false negatives. If we had the lock and found
* nothing we are done, otherwise retry with the mmap lock acquired.
*/
if (p) {
return p->flags;
} else if (have_mmap_lock()) {
return 0;
}
mmap_lock();
p = pageflags_find(address, address);
mmap_unlock();
return p ? p->flags : 0;
}
Ok, I can use this. In for v3.
As for page_get_target_data, see v2, in which there has been clean up.
r~
