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| author | Russ Cox <rsc@golang.org> | 2017-10-25 11:13:23 -0400 |
|---|---|---|
| committer | Russ Cox <rsc@golang.org> | 2017-10-25 20:23:44 +0000 |
| commit | 9be38a15e486f09663cf324539e2cb5045d54d80 (patch) | |
| tree | b3c544990984c6ecc1d65dfcc6b1cdda2c1b53a2 | |
| parent | 8bb333a9c0945666e7b2e162f85a5fff74ccf1b4 (diff) | |
| download | go-9be38a15e486f09663cf324539e2cb5045d54d80.tar.gz go-9be38a15e486f09663cf324539e2cb5045d54d80.zip | |
[release-branch.go1.9] runtime: avoid monotonic time zero on systems with low-res timers
Otherwise low-res timers cause problems at call sites that expect to
be able to use 0 as meaning "no time set" and therefore expect that
nanotime never returns 0 itself. For example, sched.lastpoll == 0
means no last poll.
Fixes #22394.
Change-Id: Iea28acfddfff6f46bc90f041ec173e0fea591285
Reviewed-on: https://go-review.googlesource.com/73410
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-on: https://go-review.googlesource.com/73491
TryBot-Result: Russ Cox <rsc@golang.org>
| -rw-r--r-- | src/runtime/proc.go | 3 | ||||
| -rw-r--r-- | src/runtime/time.go | 8 |
2 files changed, 10 insertions, 1 deletions
diff --git a/src/runtime/proc.go b/src/runtime/proc.go index a631a016a3..5787991f07 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -142,6 +142,9 @@ func main() { } runtime_init() // must be before defer + if nanotime() == 0 { + throw("nanotime returning zero") + } // Defer unlock so that runtime.Goexit during init does the unlock too. needUnlock := true diff --git a/src/runtime/time.go b/src/runtime/time.go index abf200d7d3..23f61d62d0 100644 --- a/src/runtime/time.go +++ b/src/runtime/time.go @@ -309,4 +309,10 @@ func time_runtimeNano() int64 { return nanotime() } -var startNano int64 = nanotime() +// Monotonic times are reported as offsets from startNano. +// We initialize startNano to nanotime() - 1 so that on systems where +// monotonic time resolution is fairly low (e.g. Windows 2008 +// which appears to have a default resolution of 15ms), +// we avoid ever reporting a nanotime of 0. +// (Callers may want to use 0 as "time not set".) +var startNano int64 = nanotime() - 1 |