From da153354b2862c1f7e1a55ad98680386d1fe31ef Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Tue, 16 Feb 2016 12:23:33 -0500 Subject: [PATCH] runtime: copy stack before adjusting Currently copystack adjusts pointers in the old stack and then copies the adjusted stack to the new stack. In addition to being generally confusing, this is going to make concurrent stack shrinking harder. Switch this around so that we first copy the stack and then adjust pointers on the new stack (never writing to the old stack). This reprises CL 15996, but takes a different and simpler approach. CL 15996 still walked the old stack while adjusting pointers on the new stack. In this CL, we adjust auxiliary structures before walking the stack, so we can just walk the new stack. For #12967. Change-Id: I94fa86f823ba9ee478e73b2ba509eed3361c43df Reviewed-on: https://go-review.googlesource.com/20033 Reviewed-by: Rick Hudson --- src/runtime/stack.go | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/src/runtime/stack.go b/src/runtime/stack.go index b89dc59142..d37bc7d08b 100644 --- a/src/runtime/stack.go +++ b/src/runtime/stack.go @@ -748,29 +748,27 @@ func copystack(gp *g, newsize uintptr) { print("copystack gp=", gp, " [", hex(old.lo), " ", hex(old.hi-used), " ", hex(old.hi), "]/", gp.stackAlloc, " -> [", hex(new.lo), " ", hex(new.hi-used), " ", hex(new.hi), "]/", newsize, "\n") } - // Disallow sigprof scans of this stack and block if there's - // one in progress. - gcLockStackBarriers(gp) - - // adjust pointers in the to-be-copied frames + // Compute adjustment. var adjinfo adjustinfo adjinfo.old = old adjinfo.delta = new.hi - old.hi - gentraceback(^uintptr(0), ^uintptr(0), 0, gp, 0, nil, 0x7fffffff, adjustframe, noescape(unsafe.Pointer(&adjinfo)), 0) - // adjust other miscellaneous things that have pointers into stacks. + // copy the stack to the new location + memmove(unsafe.Pointer(new.hi-used), unsafe.Pointer(old.hi-used), used) + + // Disallow sigprof scans of this stack and block if there's + // one in progress. + gcLockStackBarriers(gp) + + // Adjust structures that have pointers into stacks. We have + // to do most of these before we traceback the new stack + // because gentraceback uses them. adjustctxt(gp, &adjinfo) adjustdefers(gp, &adjinfo) adjustpanics(gp, &adjinfo) adjustsudogs(gp, &adjinfo) adjuststkbar(gp, &adjinfo) - // copy the stack to the new location - if stackPoisonCopy != 0 { - fillstack(new, 0xfb) - } - memmove(unsafe.Pointer(new.hi-used), unsafe.Pointer(old.hi-used), used) - // copy old stack barriers to new stack barrier array newstkbar = newstkbar[:len(gp.stkbar)] copy(newstkbar, gp.stkbar) @@ -784,6 +782,9 @@ func copystack(gp *g, newsize uintptr) { gp.stkbar = newstkbar gp.stktopsp += adjinfo.delta + // Adjust pointers in the new stack. + gentraceback(^uintptr(0), ^uintptr(0), 0, gp, 0, nil, 0x7fffffff, adjustframe, noescape(unsafe.Pointer(&adjinfo)), 0) + gcUnlockStackBarriers(gp) // free old stack -- 2.48.1