fix epoll single pass code and add wait-exclusive flag

Fixes the epoll single pass code.  During the unlocked event delivery (to
userspace) code, the poll callback can re-issue new events, and we must
receive them correctly.  Since we loop in a lockless fashion, we want to be
O(nready), and we don't want to flash on/off the spinlock for every event, we
have the poll callback to use a secondary list to queue events while we're
inside the event delivery loop.  The rw_semaphore has been turned into a
mutex.  This patch also adds the wait-exclusive flag, as suggested by Davi
Arnaut.

Signed-off-by: Davide Libenzi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
1 file changed