diff options
Diffstat (limited to 'src/runtime/stack.go')
| -rw-r--r-- | src/runtime/stack.go | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/src/runtime/stack.go b/src/runtime/stack.go index 2fedaa9421..67a394cd12 100644 --- a/src/runtime/stack.go +++ b/src/runtime/stack.go @@ -1075,6 +1075,29 @@ func newstack() { gopreempt_m(gp) // never return } + if stackguard0 == gp.stack.lo+stackGuard && gp.preemptRecent { + // The case happens because of an interaction between synchronous + // and asynchronous preemption. First, we set the cooperative + // preemption signal (g.stackguard0 = stackPreempt), and as a + // result the function fails the stack check and enters its + // morestack path. If it gets suspended at that point, we might + // give up waiting for it and send an async preempt. That async + // preempt gets processed and clears the cooperative preemption + // signal (g.stackguard0 = g.stack.lo+stackGuard) and resumes + // the function. But even though the cooperative preemption + // signal is cleared, we're already on the morestack path and + // can't avoid calling morestack. See issue 35470. + // + // To avoid this problem, if we've been preempted recently, + // clear the "preempted recently" flag and resume the G. + // If we really did need more stack, the morestack check will + // immediately fail and we'll get back here to try again (with + // preemptRecent==false, so we don't take this case the + // second time). + gp.preemptRecent = false + gogo(&gp.sched) // never return + } + // Allocate a bigger segment and move the stack. oldsize := gp.stack.hi - gp.stack.lo newsize := oldsize * 2 |