From: Austin Clements Date: Fri, 9 Jan 2015 19:00:40 +0000 (-0500) Subject: runtime: add GODEBUG=gccheckmark=0/1 X-Git-Tag: go1.5beta1~2379 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=654297cb0233d0af84c8d5dbf18f46b1bcdcee85;p=gostls13.git runtime: add GODEBUG=gccheckmark=0/1 Previously, gccheckmark could only be enabled or disabled by calling runtime.GCcheckmarkenable/GCcheckmarkdisable. This was a necessary hack because GODEBUG was broken. Now that GODEBUG works again, move control over gccheckmark to a GODEBUG variable and remove these runtime functions. Currently, gccheckmark is enabled by default (and will probably remain so for much of the 1.5 development cycle). Change-Id: I2bc6f30c21b795264edf7dbb6bd7354b050673ab Reviewed-on: https://go-review.googlesource.com/2603 Reviewed-by: Rick Hudson --- diff --git a/api/next.txt b/api/next.txt index b94bda13e2..eb21e80c27 100644 --- a/api/next.txt +++ b/api/next.txt @@ -247,5 +247,3 @@ pkg runtime (openbsd-amd64-cgo), const EWOULDBLOCK = 35 pkg runtime (openbsd-amd64-cgo), const EWOULDBLOCK ideal-int pkg runtime (openbsd-amd64-cgo), const HW_NCPU = 3 pkg runtime (openbsd-amd64-cgo), const HW_NCPU ideal-int -pkg runtime, func GCcheckmarkdisable() -pkg runtime, func GCcheckmarkenable() diff --git a/src/runtime/extern.go b/src/runtime/extern.go index f295b9b12c..58acbb3788 100644 --- a/src/runtime/extern.go +++ b/src/runtime/extern.go @@ -66,6 +66,12 @@ a comma-separated list of name=val pairs. Supported names are: problem with allocfreetrace=1 in order to understand the type of the badly updated word. + gccheckmark: setting gccheckmark=1 enables verification of the + garbage collector's concurrent mark phase by performing a + second mark pass while the world is stopped. If the second + pass finds a reachable object that was not found by concurrent + mark, the garbage collector will panic. + The GOMAXPROCS variable limits the number of operating system threads that can execute user-level Go code simultaneously. There is no limit to the number of threads that can be blocked in system calls on behalf of Go code; those do not count against diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go index bc14d2222d..fa59ce41e4 100644 --- a/src/runtime/malloc.go +++ b/src/runtime/malloc.go @@ -611,14 +611,6 @@ func gcwork(force int32) { } } -func GCcheckmarkenable() { - systemstack(gccheckmarkenable_m) -} - -func GCcheckmarkdisable() { - systemstack(gccheckmarkdisable_m) -} - // gctimes records the time in nanoseconds of each phase of the concurrent GC. type gctimes struct { sweepterm int64 // stw diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go index 4d0900a41c..6d2470d39a 100644 --- a/src/runtime/mgc.go +++ b/src/runtime/mgc.go @@ -236,10 +236,7 @@ func have_cgo_allocate() bool { // When marking an object if the bool checkmark is true one uses the above // encoding, otherwise one uses the bitMarked bit in the lower two bits // of the nibble. -var ( - checkmark = false - gccheckmarkenable = true -) +var checkmark = false // inheap reports whether b is a pointer into a (potentially dead) heap object. // It returns false for pointers into stack spans. @@ -559,7 +556,7 @@ func scanobject(b, n uintptr, ptrmask *uint8, wbuf *workbuf) *workbuf { continue } - if mheap_.shadow_enabled && debug.wbshadow >= 2 && gccheckmarkenable && checkmark { + if mheap_.shadow_enabled && debug.wbshadow >= 2 && debug.gccheckmark > 0 && checkmark { checkwbshadow((*uintptr)(unsafe.Pointer(b + i))) } @@ -1856,7 +1853,7 @@ func clearcheckmarkbits() { // bitMarked bit that is not set then we throw. //go:nowritebarrier func gccheckmark_m(startTime int64, eagersweep bool) { - if !gccheckmarkenable { + if debug.gccheckmark == 0 { return } @@ -1869,16 +1866,6 @@ func gccheckmark_m(startTime int64, eagersweep bool) { gc_m(startTime, eagersweep) // turns off checkmark + calls clearcheckmarkbits } -//go:nowritebarrier -func gccheckmarkenable_m() { - gccheckmarkenable = true -} - -//go:nowritebarrier -func gccheckmarkdisable_m() { - gccheckmarkenable = false -} - //go:nowritebarrier func finishsweep_m() { // The world is stopped so we should be able to complete the sweeps @@ -1987,6 +1974,9 @@ func gc(start_time int64, eagersweep bool) { } if !checkmark { + // TODO(austin) This is a noop beceause we should + // already have swept everything to the current + // sweepgen. finishsweep_m() // skip during checkmark debug phase. } @@ -2107,7 +2097,7 @@ func gc(start_time int64, eagersweep bool) { sysFree(unsafe.Pointer(&work.spans[0]), uintptr(len(work.spans))*unsafe.Sizeof(work.spans[0]), &memstats.other_sys) } - if gccheckmarkenable { + if debug.gccheckmark > 0 { if !checkmark { // first half of two-pass; don't set up sweep unlock(&mheap_.lock) diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go index e6510a8aa3..6056a8dd7e 100644 --- a/src/runtime/runtime1.go +++ b/src/runtime/runtime1.go @@ -317,6 +317,7 @@ var debug struct { scheddetail int32 schedtrace int32 wbshadow int32 + gccheckmark int32 } var dbgvars = []dbgVar{ @@ -329,9 +330,13 @@ var dbgvars = []dbgVar{ {"scheddetail", &debug.scheddetail}, {"schedtrace", &debug.schedtrace}, {"wbshadow", &debug.wbshadow}, + {"gccheckmark", &debug.gccheckmark}, } func parsedebugvars() { + // gccheckmark is enabled by default for the 1.5 dev cycle + debug.gccheckmark = 1 + for p := gogetenv("GODEBUG"); p != ""; { field := "" i := index(p, ",")