runtime: don't call wakeNetPoller during timerModifying

Reduce the length of time that other timer functions can see timerModifying.
In particular avoid system calls.

Fixes #38023

Change-Id: I1b61229c668e6085d9ee6dca9488a90055386c36
Reviewed-on: https://go-review.googlesource.com/c/go/+/224902
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

diff --git a/src/runtime/time.go b/src/runtime/time.go
index c62207d7f7b133533ffd67b80976b8ed749ffdfe..50e3d4b60bd11644f16e6c07a451b9e648dee394 100644 (file)
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -251,11 +251,6 @@ func addtimer(t *timer) {
        }
        t.status = timerWaiting
 
-       addInitializedTimer(t)
-}
-
-// addInitializedTimer adds an initialized timer to the current P.
-func addInitializedTimer(t *timer) {
        when := t.when
 
        pp := getg().m.p.ptr()
@@ -268,7 +263,6 @@ func addInitializedTimer(t *timer) {
 }
 
 // doaddtimer adds t to the current P's heap.
-// It reports whether it saw no problems due to races.
 // The caller must have locked the timers for pp.
 func doaddtimer(pp *p, t *timer) {
        // Timers rely on the network poller, so make sure the poller
@@ -443,10 +437,14 @@ loop:
 
        if wasRemoved {
                t.when = when
-               addInitializedTimer(t)
+               pp := getg().m.p.ptr()
+               lock(&pp.timersLock)
+               doaddtimer(pp, t)
+               unlock(&pp.timersLock)
                if !atomic.Cas(&t.status, timerModifying, timerWaiting) {
                        badTimer()
                }
+               wakeNetPoller(when)
        } else {
                // The timer is in some other P's heap, so we can't change
                // the when field. If we did, the other P's heap would