From c9986d1452f3ef226bfd044fb0f128175a7dff03 Mon Sep 17 00:00:00 2001 From: Heschi Kreinick Date: Fri, 17 Aug 2018 16:32:02 -0400 Subject: [PATCH] runtime: fix use of wrong g in gentraceback gentraceback gets the currently running g to do some sanity checks, but should use gp everywhere to do its actual work. Some noncritical checks later accidentally used g instead of gp. This seems like it could be a problem in many different contexts, but I noticed in Windows profiling, where profilem calls gentraceback on a goroutine from a different thread. Change-Id: I3da27a43e833b257f6411ee6893bdece45a9323f Reviewed-on: https://go-review.googlesource.com/128895 Run-TryBot: Heschi Kreinick Reviewed-by: Austin Clements --- src/runtime/traceback.go | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go index a1f32016b9..78589f5ea3 100644 --- a/src/runtime/traceback.go +++ b/src/runtime/traceback.go @@ -99,8 +99,9 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in if skip > 0 && callback != nil { throw("gentraceback callback cannot be used with non-zero skip") } - g := getg() - if g == gp && g == g.m.curg { + + // Don't call this "g"; it's too easy get "g" and "gp" confused. + if ourg := getg(); ourg == gp && ourg == ourg.m.curg { // The starting sp has been passed in as a uintptr, and the caller may // have other uintptr-typed stack references as well. // If during one of the calls that got us here or during one of the @@ -200,7 +201,7 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in // g0, this systemstack is at the top of the stack. // if we're not on g0 or there's a no curg, then this is a regular call. sp := frame.sp - if flags&_TraceJumpStack != 0 && f.funcID == funcID_systemstack && gp == g.m.g0 && gp.m.curg != nil { + if flags&_TraceJumpStack != 0 && f.funcID == funcID_systemstack && gp == gp.m.g0 && gp.m.curg != nil { sp = gp.m.curg.sched.sp frame.sp = sp cgoCtxt = gp.m.curg.cgoCtxt @@ -425,7 +426,7 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in if frame.pc > f.entry { print(" +", hex(frame.pc-f.entry)) } - if g.m.throwing > 0 && gp == g.m.curg || level >= 2 { + if gp.m != nil && gp.m.throwing > 0 && gp == gp.m.curg || level >= 2 { print(" fp=", hex(frame.fp), " sp=", hex(frame.sp), " pc=", hex(frame.pc)) } print("\n") -- 2.50.0