Merge branch 'pipe-exclusive-wakeup'
Merge thundering herd avoidance on pipe IO. This would have been applied for 5.5 already, but got delayed because of a user-space race condition in the GNU make jobserver code. Now that there's a new GNU make 4.3 release, and most distributions seem to have at least applied the (almost three year old) fix for the problem, let's see if people notice. And it might have been just bad random timing luck on my machine. If you do hit the race condition, things will still work, but the symptom is that you don't get nearly the expected parallelism when using "make -j<N>". The jobserver bug can definitely happen without this patch too, but seems to be easier to trigger when we no longer wake up pipe waiters unnecessarily. * pipe-exclusive-wakeup: pipe: use exclusive waits when reading or writing