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| author | Carlo Alberto Ferraris <cafxx@strayorange.com> | 2019-10-02 19:15:53 +0900 |
|---|---|---|
| committer | Ian Lance Taylor <iant@golang.org> | 2019-11-07 05:59:33 +0000 |
| commit | a8f57f4adad2122b42ea05024b61e93442788289 (patch) | |
| tree | e67255dc5bf1aebc30f7ffdaccf1c80980474ee8 /src/sync | |
| parent | 3eabdd291d3f53c88fdd01aca30158d0c06420b6 (diff) | |
| download | go-a8f57f4adad2122b42ea05024b61e93442788289.tar.gz go-a8f57f4adad2122b42ea05024b61e93442788289.zip | |
sync: yield to the waiter when unlocking a starving mutex
When we have already assigned the semaphore ticket to a specific
waiter, we want to get the waiter running as fast as possible since
no other G waiting on the semaphore can acquire it optimistically.
The net effect is that, when a sync.Mutex is contented, the code in
the critical section guarded by the Mutex gets a priority boost.
Fixes #33747
Change-Id: I9967f0f763c25504010651bdd7f944ee0189cd45
Reviewed-on: https://go-review.googlesource.com/c/go/+/200577
Reviewed-by: Rhys Hiltner <rhys@justin.tv>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Diffstat (limited to 'src/sync')
| -rw-r--r-- | src/sync/mutex.go | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/sync/mutex.go b/src/sync/mutex.go index 11ad20c975..3028552f74 100644 --- a/src/sync/mutex.go +++ b/src/sync/mutex.go @@ -216,7 +216,8 @@ func (m *Mutex) unlockSlow(new int32) { old = m.state } } else { - // Starving mode: handoff mutex ownership to the next waiter. + // Starving mode: handoff mutex ownership to the next waiter, and yield + // our time slice so that the next waiter can start to run immediately. // Note: mutexLocked is not set, the waiter will set it after wakeup. // But mutex is still considered locked if mutexStarving is set, // so new coming goroutines won't acquire it. |