[dev.cc] runtime: convert parallel support code from C to Go

The conversion was done with an automated tool and then
modified only as necessary to make it compile and run.

[This CL is part of the removal of C code from package runtime.
See golang.org/s/dev.cc for an overview.]

LGTM=r
R=r, austin
CC=dvyukov, golang-codereviews, iant, khr
https://golang.org/cl/172250043

src/runtime/export_test.go

@@ -34,21 +34,11 @@ func lfstackpush_m()
 func lfstackpop_m()
 
 func LFStackPush(head *uint64, node *LFNode) {
-	mp := acquirem()
-	mp.ptrarg[0] = unsafe.Pointer(head)
-	mp.ptrarg[1] = unsafe.Pointer(node)
-	onM(lfstackpush_m)
-	releasem(mp)
+	lfstackpush(head, (*lfnode)(unsafe.Pointer(node)))
 }
 
 func LFStackPop(head *uint64) *LFNode {
-	mp := acquirem()
-	mp.ptrarg[0] = unsafe.Pointer(head)
-	onM(lfstackpop_m)
-	node := (*LFNode)(unsafe.Pointer(mp.ptrarg[0]))
-	mp.ptrarg[0] = nil
-	releasem(mp)
-	return node
+	return (*LFNode)(unsafe.Pointer(lfstackpop(head)))
 }
 
 type ParFor struct {
@@ -68,64 +58,44 @@ func parfordo_m()
 func parforiters_m()
 
 func NewParFor(nthrmax uint32) *ParFor {
-	mp := acquirem()
-	mp.scalararg[0] = uintptr(nthrmax)
-	onM(newparfor_m)
-	desc := (*ParFor)(mp.ptrarg[0])
-	mp.ptrarg[0] = nil
-	releasem(mp)
+	var desc *ParFor
+	onM(func() {
+		desc = (*ParFor)(unsafe.Pointer(parforalloc(nthrmax)))
+	})
 	return desc
 }
 
 func ParForSetup(desc *ParFor, nthr, n uint32, ctx *byte, wait bool, body func(*ParFor, uint32)) {
-	mp := acquirem()
-	mp.ptrarg[0] = unsafe.Pointer(desc)
-	mp.ptrarg[1] = unsafe.Pointer(ctx)
-	mp.ptrarg[2] = unsafe.Pointer(funcPC(body)) // TODO(rsc): Should be a scalar.
-	mp.scalararg[0] = uintptr(nthr)
-	mp.scalararg[1] = uintptr(n)
-	mp.scalararg[2] = 0
-	if wait {
-		mp.scalararg[2] = 1
-	}
-	onM(parforsetup_m)
-	releasem(mp)
+	onM(func() {
+		parforsetup((*parfor)(unsafe.Pointer(desc)), nthr, n, unsafe.Pointer(ctx), wait,
+			*(*func(*parfor, uint32))(unsafe.Pointer(&body)))
+	})
 }
 
 func ParForDo(desc *ParFor) {
-	mp := acquirem()
-	mp.ptrarg[0] = unsafe.Pointer(desc)
-	onM(parfordo_m)
-	releasem(mp)
+	onM(func() {
+		parfordo((*parfor)(unsafe.Pointer(desc)))
+	})
 }
 
 func ParForIters(desc *ParFor, tid uint32) (uint32, uint32) {
-	mp := acquirem()
-	mp.ptrarg[0] = unsafe.Pointer(desc)
-	mp.scalararg[0] = uintptr(tid)
-	onM(parforiters_m)
-	begin := uint32(mp.scalararg[0])
-	end := uint32(mp.scalararg[1])
-	releasem(mp)
-	return begin, end
+	desc1 := (*parfor)(unsafe.Pointer(desc))
+	pos := desc_thr_index(desc1, tid).pos
+	return uint32(pos), uint32(pos >> 32)
 }
 
-// in mgc0.c
-//go:noescape
-func getgcmask(data unsafe.Pointer, typ *_type, array **byte, len *uint)
-
 func GCMask(x interface{}) (ret []byte) {
 	e := (*eface)(unsafe.Pointer(&x))
 	s := (*slice)(unsafe.Pointer(&ret))
 	onM(func() {
-		getgcmask(e.data, e._type, &s.array, &s.len)
+		var len uintptr
+		getgcmask(e.data, e._type, &s.array, &len)
+		s.len = uint(len)
 		s.cap = s.len
 	})
 	return
 }
 
-func testSchedLocalQueue()
-func testSchedLocalQueueSteal()
 func RunSchedLocalQueueTest() {
 	onM(testSchedLocalQueue)
 }
@@ -149,10 +119,6 @@ func GogoBytes() int32 {
 	return _RuntimeGogoBytes
 }
 
-// in string.c
-//go:noescape
-func gostringw(w *uint16) string
-
 // entry point for testing
 func GostringW(w []uint16) (s string) {
 	onM(func() {

src/runtime/lfstack.c

-// Copyright 2012 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Lock-free stack.
-// The following code runs only on g0 stack.
-
-#include "runtime.h"
-#include "arch_GOARCH.h"
-
-#ifdef _64BIT
-// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
-// So we use 17msb of pointers as ABA counter.
-# define PTR_BITS 47
-#else
-# define PTR_BITS 32
-#endif
-#define PTR_MASK ((1ull<<PTR_BITS)-1)
-#define CNT_MASK (0ull-1)
-
-#ifdef _64BIT
-#ifdef GOOS_solaris
-// SPARC64 and Solaris on AMD64 uses all 64 bits of virtual addresses.
-// Use low-order three bits as ABA counter.
-// http://docs.oracle.com/cd/E19120-01/open.solaris/816-5138/6mba6ua5p/index.html
-#undef PTR_BITS
-#undef CNT_MASK
-#undef PTR_MASK
-#define PTR_BITS 0
-#define CNT_MASK 7
-#define PTR_MASK ((0ull-1)<<3)
-#endif
-#endif
-
-void
-runtime·lfstackpush(uint64 *head, LFNode *node)
-{
-	uint64 old, new;
-
-	if((uintptr)node != ((uintptr)node&PTR_MASK)) {
-		runtime·printf("p=%p\n", node);
-		runtime·throw("runtime·lfstackpush: invalid pointer");
-	}
-
-	node->pushcnt++;
-	new = (uint64)(uintptr)node|(((uint64)node->pushcnt&CNT_MASK)<<PTR_BITS);
-	for(;;) {
-		old = runtime·atomicload64(head);
-		node->next = (LFNode*)(uintptr)(old&PTR_MASK);
-		if(runtime·cas64(head, old, new))
-			break;
-	}
-}
-
-LFNode*
-runtime·lfstackpop(uint64 *head)
-{
-	LFNode *node, *node2;
-	uint64 old, new;
-
-	for(;;) {
-		old = runtime·atomicload64(head);
-		if(old == 0)
-			return nil;
-		node = (LFNode*)(uintptr)(old&PTR_MASK);
-		node2 = runtime·atomicloadp(&node->next);
-		new = 0;
-		if(node2 != nil)
-			new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt&CNT_MASK)<<PTR_BITS);
-		if(runtime·cas64(head, old, new))
-			return node;
-	}
-}
-
-void
-runtime·lfstackpush_m(void)
-{
-	runtime·lfstackpush(g->m->ptrarg[0], g->m->ptrarg[1]);
-	g->m->ptrarg[0] = nil;
-	g->m->ptrarg[1] = nil;
-}
-
-void
-runtime·lfstackpop_m(void)
-{
-	g->m->ptrarg[0] = runtime·lfstackpop(g->m->ptrarg[0]);
-}

src/runtime/lfstack.go

+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Lock-free stack.
+// The following code runs only on g0 stack.
+
+package runtime
+
+import "unsafe"
+
+const (
+	// lfPtrBits and lfCountMask are defined in lfstack_*.go.
+	lfPtrMask = 1<<lfPtrBits - 1
+)
+
+func lfstackpush(head *uint64, node *lfnode) {
+	unode := uintptr(unsafe.Pointer(node))
+	if unode&^lfPtrMask != 0 {
+		print("p=", node, "\n")
+		gothrow("lfstackpush: invalid pointer")
+	}
+
+	node.pushcnt++
+	new := uint64(unode) | (uint64(node.pushcnt)&lfCountMask)<<lfPtrBits
+	for {
+		old := atomicload64(head)
+		node.next = (*lfnode)(unsafe.Pointer(uintptr(old & lfPtrMask)))
+		if cas64(head, old, new) {
+			break
+		}
+	}
+}
+
+func lfstackpop(head *uint64) unsafe.Pointer {
+	for {
+		old := atomicload64(head)
+		if old == 0 {
+			return nil
+		}
+		node := (*lfnode)(unsafe.Pointer(uintptr(old & lfPtrMask)))
+		node2 := (*lfnode)(atomicloadp(unsafe.Pointer(&node.next)))
+		new := uint64(0)
+		if node2 != nil {
+			new = uint64(uintptr(unsafe.Pointer(node2))) | uint64(node2.pushcnt&lfCountMask)<<lfPtrBits
+		}
+		if cas64(head, old, new) {
+			return unsafe.Pointer(node)
+		}
+	}
+}

src/runtime/lfstack_32bit.go

+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build 386 arm
+
+package runtime
+
+// On 32-bit systems, the stored uint64 has a 32-bit pointer and 32-bit count.
+const (
+	lfPtrBits   = 32
+	lfCountMask = 1<<32 - 1
+)

src/runtime/lfstack_amd64.go

+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
+// So we use 17msb of pointers as ABA counter.
+const (
+	lfPtrBits   = 47
+	lfCountMask = 1<<17 - 1
+)

src/runtime/parfor.c

-// Copyright 2012 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Parallel for algorithm.
-
-#include "runtime.h"
-#include "arch_GOARCH.h"
-#include "malloc.h"
-
-struct ParForThread
-{
-	// the thread's iteration space [32lsb, 32msb)
-	uint64 pos;
-	// stats
-	uint64 nsteal;
-	uint64 nstealcnt;
-	uint64 nprocyield;
-	uint64 nosyield;
-	uint64 nsleep;
-	byte pad[CacheLineSize];
-};
-
-void
-runtime·parforsetup(ParFor *desc, uint32 nthr, uint32 n, void *ctx, bool wait, void (*body)(ParFor*, uint32))
-{
-	uint32 i, begin, end;
-	uint64 *pos;
-
-	if(desc == nil || nthr == 0 || nthr > desc->nthrmax || body == nil) {
-		runtime·printf("desc=%p nthr=%d count=%d body=%p\n", desc, nthr, n, body);
-		runtime·throw("parfor: invalid args");
-	}
-
-	desc->body = body;
-	desc->done = 0;
-	desc->nthr = nthr;
-	desc->thrseq = 0;
-	desc->cnt = n;
-	desc->ctx = ctx;
-	desc->wait = wait;
-	desc->nsteal = 0;
-	desc->nstealcnt = 0;
-	desc->nprocyield = 0;
-	desc->nosyield = 0;
-	desc->nsleep = 0;
-	for(i=0; i<nthr; i++) {
-		begin = (uint64)n*i / nthr;
-		end = (uint64)n*(i+1) / nthr;
-		pos = &desc->thr[i].pos;
-		if(((uintptr)pos & 7) != 0)
-			runtime·throw("parforsetup: pos is not aligned");
-		*pos = (uint64)begin | (((uint64)end)<<32);
-	}
-}
-
-void
-runtime·parfordo(ParFor *desc)
-{
-	ParForThread *me;
-	uint32 tid, begin, end, begin2, try, victim, i;
-	uint64 *mypos, *victimpos, pos, newpos;
-	void (*body)(ParFor*, uint32);
-	bool idle;
-
-	// Obtain 0-based thread index.
-	tid = runtime·xadd(&desc->thrseq, 1) - 1;
-	if(tid >= desc->nthr) {
-		runtime·printf("tid=%d nthr=%d\n", tid, desc->nthr);
-		runtime·throw("parfor: invalid tid");
-	}
-
-	// If single-threaded, just execute the for serially.
-	if(desc->nthr==1) {
-		for(i=0; i<desc->cnt; i++)
-			desc->body(desc, i);
-		return;
-	}
-
-	body = desc->body;
-	me = &desc->thr[tid];
-	mypos = &me->pos;
-	for(;;) {
-		for(;;) {
-			// While there is local work,
-			// bump low index and execute the iteration.
-			pos = runtime·xadd64(mypos, 1);
-			begin = (uint32)pos-1;
-			end = (uint32)(pos>>32);
-			if(begin < end) {
-				body(desc, begin);
-				continue;
-			}
-			break;
-		}
-
-		// Out of work, need to steal something.
-		idle = false;
-		for(try=0;; try++) {
-			// If we don't see any work for long enough,
-			// increment the done counter...
-			if(try > desc->nthr*4 && !idle) {
-				idle = true;
-				runtime·xadd(&desc->done, 1);
-			}
-			// ...if all threads have incremented the counter,
-			// we are done.
-			if(desc->done + !idle == desc->nthr) {
-				if(!idle)
-					runtime·xadd(&desc->done, 1);
-				goto exit;
-			}
-			// Choose a random victim for stealing.
-			victim = runtime·fastrand1() % (desc->nthr-1);
-			if(victim >= tid)
-				victim++;
-			victimpos = &desc->thr[victim].pos;
-			for(;;) {
-				// See if it has any work.
-				pos = runtime·atomicload64(victimpos);
-				begin = (uint32)pos;
-				end = (uint32)(pos>>32);
-				if(begin+1 >= end) {
-					begin = end = 0;
-					break;
-				}
-				if(idle) {
-					runtime·xadd(&desc->done, -1);
-					idle = false;
-				}
-				begin2 = begin + (end-begin)/2;
-				newpos = (uint64)begin | (uint64)begin2<<32;
-				if(runtime·cas64(victimpos, pos, newpos)) {
-					begin = begin2;
-					break;
-				}
-			}
-			if(begin < end) {
-				// Has successfully stolen some work.
-				if(idle)
-					runtime·throw("parfor: should not be idle");
-				runtime·atomicstore64(mypos, (uint64)begin | (uint64)end<<32);
-				me->nsteal++;
-				me->nstealcnt += end-begin;
-				break;
-			}
-			// Backoff.
-			if(try < desc->nthr) {
-				// nothing
-			} else if (try < 4*desc->nthr) {
-				me->nprocyield++;
-				runtime·procyield(20);
-			// If a caller asked not to wait for the others, exit now
-			// (assume that most work is already done at this point).
-			} else if (!desc->wait) {
-				if(!idle)
-					runtime·xadd(&desc->done, 1);
-				goto exit;
-			} else if (try < 6*desc->nthr) {
-				me->nosyield++;
-				runtime·osyield();
-			} else {
-				me->nsleep++;
-				runtime·usleep(1);
-			}
-		}
-	}
-exit:
-	runtime·xadd64(&desc->nsteal, me->nsteal);
-	runtime·xadd64(&desc->nstealcnt, me->nstealcnt);
-	runtime·xadd64(&desc->nprocyield, me->nprocyield);
-	runtime·xadd64(&desc->nosyield, me->nosyield);
-	runtime·xadd64(&desc->nsleep, me->nsleep);
-	me->nsteal = 0;
-	me->nstealcnt = 0;
-	me->nprocyield = 0;
-	me->nosyield = 0;
-	me->nsleep = 0;
-}
-
-// For testing from Go.
-void
-runtime·newparfor_m(void)
-{
-	g->m->ptrarg[0] = runtime·parforalloc(g->m->scalararg[0]);
-}
-
-void
-runtime·parforsetup_m(void)
-{
-	ParFor *desc;
-	void *ctx;
-	void (*body)(ParFor*, uint32);
-
-	desc = g->m->ptrarg[0];
-	g->m->ptrarg[0] = nil;
-	ctx = g->m->ptrarg[1];
-	g->m->ptrarg[1] = nil;
-	body = g->m->ptrarg[2];
-	g->m->ptrarg[2] = nil;
-
-	runtime·parforsetup(desc, g->m->scalararg[0], g->m->scalararg[1], ctx, g->m->scalararg[2], body);
-}
-
-void
-runtime·parfordo_m(void)
-{
-	ParFor *desc;
-
-	desc = g->m->ptrarg[0];
-	g->m->ptrarg[0] = nil;
-	runtime·parfordo(desc);
-}
-
-void
-runtime·parforiters_m(void)
-{
-	ParFor *desc;
-	uintptr tid;
-
-	desc = g->m->ptrarg[0];
-	g->m->ptrarg[0] = nil;
-	tid = g->m->scalararg[0];
-	g->m->scalararg[0] = desc->thr[tid].pos;
-	g->m->scalararg[1] = desc->thr[tid].pos>>32;
-}

src/runtime/parfor.go

+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Parallel for algorithm.
+
+package runtime
+
+import "unsafe"
+
+type parforthread struct {
+	// the thread's iteration space [32lsb, 32msb)
+	pos uint64
+	// stats
+	nsteal     uint64
+	nstealcnt  uint64
+	nprocyield uint64
+	nosyield   uint64
+	nsleep     uint64
+	pad        [_CacheLineSize]byte
+}
+
+func desc_thr_index(desc *parfor, i uint32) *parforthread {
+	return (*parforthread)(add(unsafe.Pointer(desc.thr), uintptr(i)*unsafe.Sizeof(*desc.thr)))
+}
+
+func parforsetup(desc *parfor, nthr, n uint32, ctx unsafe.Pointer, wait bool, body func(*parfor, uint32)) {
+	if desc == nil || nthr == 0 || nthr > desc.nthrmax || body == nil {
+		print("desc=", desc, " nthr=", nthr, " count=", n, " body=", body, "\n")
+		gothrow("parfor: invalid args")
+	}
+
+	desc.body = *(*unsafe.Pointer)(unsafe.Pointer(&body))
+	desc.done = 0
+	desc.nthr = nthr
+	desc.thrseq = 0
+	desc.cnt = n
+	desc.ctx = ctx
+	desc.wait = wait
+	desc.nsteal = 0
+	desc.nstealcnt = 0
+	desc.nprocyield = 0
+	desc.nosyield = 0
+	desc.nsleep = 0
+
+	for i := uint32(0); i < nthr; i++ {
+		begin := uint32(uint64(n) * uint64(i) / uint64(nthr))
+		end := uint32(uint64(n) * uint64(i+1) / uint64(nthr))
+		pos := &desc_thr_index(desc, i).pos
+		if uintptr(unsafe.Pointer(pos))&7 != 0 {
+			gothrow("parforsetup: pos is not aligned")
+		}
+		*pos = uint64(begin) | uint64(end)<<32
+	}
+}
+
+func parfordo(desc *parfor) {
+	// Obtain 0-based thread index.
+	tid := xadd(&desc.thrseq, 1) - 1
+	if tid >= desc.nthr {
+		print("tid=", tid, " nthr=", desc.nthr, "\n")
+		gothrow("parfor: invalid tid")
+	}
+
+	// If single-threaded, just execute the for serially.
+	body := *(*func(*parfor, uint32))(unsafe.Pointer(&desc.body))
+	if desc.nthr == 1 {
+		for i := uint32(0); i < desc.cnt; i++ {
+			body(desc, i)
+		}
+		return
+	}
+
+	me := desc_thr_index(desc, tid)
+	mypos := &me.pos
+	for {
+		for {
+			// While there is local work,
+			// bump low index and execute the iteration.
+			pos := xadd64(mypos, 1)
+			begin := uint32(pos) - 1
+			end := uint32(pos >> 32)
+			if begin < end {
+				body(desc, begin)
+				continue
+			}
+			break
+		}
+
+		// Out of work, need to steal something.
+		idle := false
+		for try := uint32(0); ; try++ {
+			// If we don't see any work for long enough,
+			// increment the done counter...
+			if try > desc.nthr*4 && !idle {
+				idle = true
+				xadd(&desc.done, 1)
+			}
+
+			// ...if all threads have incremented the counter,
+			// we are done.
+			extra := uint32(0)
+			if !idle {
+				extra = 1
+			}
+			if desc.done+extra == desc.nthr {
+				if !idle {
+					xadd(&desc.done, 1)
+				}
+				goto exit
+			}
+
+			// Choose a random victim for stealing.
+			var begin, end uint32
+			victim := fastrand1() % (desc.nthr - 1)
+			if victim >= tid {
+				victim++
+			}
+			victimpos := &desc_thr_index(desc, victim).pos
+			for {
+				// See if it has any work.
+				pos := atomicload64(victimpos)
+				begin = uint32(pos)
+				end = uint32(pos >> 32)
+				if begin+1 >= end {
+					end = 0
+					begin = end
+					break
+				}
+				if idle {
+					xadd(&desc.done, -1)
+					idle = false
+				}
+				begin2 := begin + (end-begin)/2
+				newpos := uint64(begin) | uint64(begin2)<<32
+				if cas64(victimpos, pos, newpos) {
+					begin = begin2
+					break
+				}
+			}
+			if begin < end {
+				// Has successfully stolen some work.
+				if idle {
+					gothrow("parfor: should not be idle")
+				}
+				atomicstore64(mypos, uint64(begin)|uint64(end)<<32)
+				me.nsteal++
+				me.nstealcnt += uint64(end) - uint64(begin)
+				break
+			}
+
+			// Backoff.
+			if try < desc.nthr {
+				// nothing
+			} else if try < 4*desc.nthr {
+				me.nprocyield++
+				procyield(20)
+			} else if !desc.wait {
+				// If a caller asked not to wait for the others, exit now
+				// (assume that most work is already done at this point).
+				if !idle {
+					xadd(&desc.done, 1)
+				}
+				goto exit
+			} else if try < 6*desc.nthr {
+				me.nosyield++
+				osyield()
+			} else {
+				me.nsleep++
+				usleep(1)
+			}
+		}
+	}
+
+exit:
+	xadd64(&desc.nsteal, int64(me.nsteal))
+	xadd64(&desc.nstealcnt, int64(me.nstealcnt))
+	xadd64(&desc.nprocyield, int64(me.nprocyield))
+	xadd64(&desc.nosyield, int64(me.nosyield))
+	xadd64(&desc.nsleep, int64(me.nsleep))
+	me.nsteal = 0
+	me.nstealcnt = 0
+	me.nprocyield = 0
+	me.nosyield = 0
+	me.nsleep = 0
+}