On 11/26/18 6:28 PM, Paolo Bonzini wrote:
On 26/11/18 09:18, Xiao Guangrong wrote:
+static uint64_t get_free_request_bitmap(Threads *threads,
ThreadLocal *thread)
+{
+ uint64_t request_fill_bitmap, request_done_bitmap, result_bitmap;
+
+ request_fill_bitmap =
atomic_rcu_read(&thread->request_fill_bitmap);
+ request_done_bitmap =
atomic_rcu_read(&thread->request_done_bitmap);
+ bitmap_xor(&result_bitmap, &request_fill_bitmap,
&request_done_bitmap,
+ threads->thread_requests_nr);
This is not wrong, but it's a big ugly. Instead, I would:
- Introduce bitmap_xor_atomic in a previous patch
- Use bitmap_xor_atomic here, getting rid of the rcu reads
Hmm, however, we do not need atomic xor operation here... that should be
slower than
just two READ_ONCE calls.
Yeah, I'd just go with Guangrong's version. Alternatively, add
find_{first,next}_{same,different}_bit functions (whatever subset of the
4 you need).
That's good to me. will try it. ;)
