diff options
Diffstat (limited to 'src/runtime/select.go')
| -rw-r--r-- | src/runtime/select.go | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/src/runtime/select.go b/src/runtime/select.go index 8033b6512f..f8f768387f 100644 --- a/src/runtime/select.go +++ b/src/runtime/select.go @@ -7,6 +7,7 @@ package runtime // This file contains the implementation of Go select statements. import ( + "runtime/internal/atomic" "unsafe" ) @@ -77,7 +78,20 @@ func selunlock(scases []scase, lockorder []uint16) { func selparkcommit(gp *g, _ unsafe.Pointer) bool { // There are unlocked sudogs that point into gp's stack. Stack // copying must lock the channels of those sudogs. + // Set activeStackChans here instead of before we try parking + // because we could self-deadlock in stack growth on a + // channel lock. gp.activeStackChans = true + // Mark that it's safe for stack shrinking to occur now, + // because any thread acquiring this G's stack for shrinking + // is guaranteed to observe activeStackChans after this store. + atomic.Store8(&gp.parkingOnChan, 0) + // Make sure we unlock after setting activeStackChans and + // unsetting parkingOnChan. The moment we unlock any of the + // channel locks we risk gp getting readied by a channel operation + // and so gp could continue running before everything before the + // unlock is visible (even to gp itself). + // This must not access gp's stack (see gopark). In // particular, it must not access the *hselect. That's okay, // because by the time this is called, gp.waiting has all @@ -313,6 +327,11 @@ loop: // wait for someone to wake us up gp.param = nil + // Signal to anyone trying to shrink our stack that we're about + // to park on a channel. The window between when this G's status + // changes and when we set gp.activeStackChans is not safe for + // stack shrinking. + atomic.Store8(&gp.parkingOnChan, 1) gopark(selparkcommit, nil, waitReasonSelect, traceEvGoBlockSelect, 1) gp.activeStackChans = false |