From 97b3ce430bb64fb6c8dfb244d400468932f2e984 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Thu, 1 Apr 2021 16:50:53 -0400 Subject: runtime: make gcTestMoveStackOnNextCall not double the stack Currently, gcTestMoveStackOnNextCall doubles the stack allocation on each call because stack movement always doubles the stack. That's rather unfortunate if you're doing a bunch of stack movement tests in a row that don't actually have to grow the stack because you'll quickly hit the stack size limit even though you're hardly using any of the stack. Fix this by adding a special stack poison value for gcTestMoveStackOnNextCall that newstack recognizes and inhibits the allocation doubling. Change-Id: Iace7055a0f33cb48dc97b8f4b46e45304bee832c Reviewed-on: https://go-review.googlesource.com/c/go/+/306672 Trust: Austin Clements Run-TryBot: Austin Clements Reviewed-by: Michael Knyszek TryBot-Result: Go Bot --- src/runtime/stack.go | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'src/runtime/stack.go') diff --git a/src/runtime/stack.go b/src/runtime/stack.go index d971e5e26f..5c7fadc2d2 100644 --- a/src/runtime/stack.go +++ b/src/runtime/stack.go @@ -132,6 +132,10 @@ const ( // Stored into g->stackguard0 to cause split stack check failure. // Must be greater than any real sp. stackFork = uintptrMask & -1234 + + // Force a stack movement. Used for debugging. + // 0xfffffeed in hex. + stackForceMove = uintptrMask & -275 ) // Global pool of spans that have free stacks. @@ -1054,11 +1058,18 @@ func newstack() { // recheck the bounds on return.) if f := findfunc(gp.sched.pc); f.valid() { max := uintptr(funcMaxSPDelta(f)) - for newsize-oldsize < max+_StackGuard { + for newsize-gp.sched.sp < max+_StackGuard { newsize *= 2 } } + if gp.stackguard0 == stackForceMove { + // Forced stack movement used for debugging. + // Don't double the stack (or we may quickly run out + // if this is done repeatedly). + newsize = oldsize + } + if newsize > maxstacksize || newsize > maxstackceiling { if maxstacksize < maxstackceiling { print("runtime: goroutine stack exceeds ", maxstacksize, "-byte limit\n") -- cgit v1.3