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| author | Michael Anthony Knyszek <mknyszek@google.com> | 2021-12-07 00:24:54 -0500 |
|---|---|---|
| committer | Michael Knyszek <mknyszek@google.com> | 2021-12-07 17:46:04 +0000 |
| commit | 4c943abb95578da4bfd70d365814a130da8d5aa2 (patch) | |
| tree | e0d4f858b936a0ebc4773b3aa197f14d2835c305 /src/runtime/testdata | |
| parent | dc65c489cc5a795a68d844ed7a45e5d16562401d (diff) | |
| download | go-4c943abb95578da4bfd70d365814a130da8d5aa2.tar.xz | |
runtime: fix comments on the behavior of SetGCPercent
Fixes for #49680, #49695, #45867, and #49370 all assumed that
SetGCPercent(-1) doesn't block until the GC's mark phase is done, but
it actually does. The cause of 3 of those 4 failures comes from the fact
that at the beginning of the sweep phase, the GC does try to preempt
every P once, and this may run concurrently with test code. In the
fourth case, the issue was likely that only *one* of the debug_test.go
tests was missing a call to SetGCPercent(-1). Just to be safe, leave a
TODO there for now to remove the extraneous runtime.GC calls, but leave
the calls in.
Updates #49680, #49695, #45867, and #49370.
Change-Id: Ibf4e64addfba18312526968bcf40f1f5d54eb3f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/369815
Reviewed-by: Austin Clements <austin@google.com>
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Diffstat (limited to 'src/runtime/testdata')
| -rw-r--r-- | src/runtime/testdata/testprog/preempt.go | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/runtime/testdata/testprog/preempt.go b/src/runtime/testdata/testprog/preempt.go index eb9f59053c..fb6755a372 100644 --- a/src/runtime/testdata/testprog/preempt.go +++ b/src/runtime/testdata/testprog/preempt.go @@ -21,7 +21,8 @@ func AsyncPreempt() { // Disable GC so we have complete control of what we're testing. debug.SetGCPercent(-1) // Out of an abundance of caution, also make sure that there are - // no GCs actively in progress. + // no GCs actively in progress. The sweep phase of a GC cycle + // for instance tries to preempt Ps at the very beginning. runtime.GC() // Start a goroutine with no sync safe-points. |