errgroup/semaphore
徐志强 43a5402ce7 semaphore: unblock waiters when the front waiter cancels
When `Release`, if the remaining tokens are not enough for the front waiter, no waiters will be notified.

So if the canceled waiter is the front one, it should try to notify following waiters if there are remaining tokens.

I found this bug when implementing a cancelable rwmutex based on semaphore:

https://github.com/zhiqiangxu/util/blob/master/mutex/crwmutex.go

This bug can be verified by this test:

https://github.com/zhiqiangxu/util/blob/master/mutex/crwmutex_test.go#L43

Change-Id: Id8564976bd375a82c4fbc6cb08b0bb83118a346c
GitHub-Last-Rev: 29b6ff26bf779d23239cfe64a395378a9e41d1fc
GitHub-Pull-Request: golang/sync#10
Reviewed-on: https://go-review.googlesource.com/c/sync/+/223418
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
2020-03-17 01:50:54 +00:00
..
semaphore.go semaphore: unblock waiters when the front waiter cancels 2020-03-17 01:50:54 +00:00
semaphore_bench_test.go all: remove x/net/context in favour of context 2018-11-08 01:04:31 +00:00
semaphore_example_test.go semaphore: add worker-pool example 2017-11-01 21:47:15 +00:00
semaphore_test.go semaphore: unblock waiters when the front waiter cancels 2020-03-17 01:50:54 +00:00