src/pkg/runtime/darwin/thread.c - go - Git at Google

 // Copyright 2009 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.

 #include "runtime.h"
 #include "defs.h"
 #include "os.h"

 static void
 unimplemented(int8 *name)
 {
 	prints(name);
 	prints(" not implemented\n");
 	*(int32*)1231 = 1231;
 }

 // Thread-safe allocation of a semaphore.
 // Psema points at a kernel semaphore key.
 // It starts out zero, meaning no semaphore.
 // Fill it in, being careful of others calling initsema
 // simultaneously.
 static void
 initsema(uint32 *psema)
 {
 	uint32 sema;

 	if(*psema != 0)	// already have one
 		return;

 	sema = mach_semcreate();
 	if(!cas(psema, 0, sema)){
 		// Someone else filled it in.  Use theirs.
 		mach_semdestroy(sema);
 		return;
 	}
 }


 // Atomic add and return new value.
 static uint32
 xadd(uint32 volatile *val, int32 delta)
 {
 	uint32 oval, nval;

 	for(;;){
 		oval = *val;
 		nval = oval + delta;
 		if(cas(val, oval, nval))
 			return nval;
 	}
 }


 // Blocking locks.

 // Implement Locks, using semaphores.
 // l->key is the number of threads who want the lock.
 // In a race, one thread increments l->key from 0 to 1
 // and the others increment it from >0 to >1.  The thread
 // who does the 0->1 increment gets the lock, and the
 // others wait on the semaphore.  When the 0->1 thread
 // releases the lock by decrementing l->key, l->key will
 // be >0, so it will increment the semaphore to wake up
 // one of the others.  This is the same algorithm used
 // in Plan 9's user-level locks.
 //
 // Note that semaphores are never destroyed (the kernel
 // will clean up when the process exits).  We assume for now
 // that Locks are only used for long-lived structures like M and G.

 void
 lock(Lock *l)
 {
 	if(m->locks < 0)
 		throw("lock count");
 	m->locks++;

 	// Allocate semaphore if needed.
 	if(l->sema == 0)
 		initsema(&l->sema);

 	if(xadd(&l->key, 1) > 1)	// someone else has it; wait
 		mach_semacquire(l->sema);
 }

 void
 unlock(Lock *l)
 {
 	m->locks--;
 	if(m->locks < 0)
 		throw("lock count");

 	if(xadd(&l->key, -1) > 0)	// someone else is waiting
 		mach_semrelease(l->sema);
 }


 // User-level semaphore implementation:
 // try to do the operations in user space on u,
 // but when it's time to block, fall back on the kernel semaphore k.
 // This is the same algorithm used in Plan 9.
 void
 usemacquire(Usema *s)
 {
 	if((int32)xadd(&s->u, -1) < 0)
 		mach_semacquire(s->k);
 }

 void
 usemrelease(Usema *s)
 {
 	if((int32)xadd(&s->u, 1) <= 0)
 		mach_semrelease(s->k);
 }


 // Event notifications.
 void
 noteclear(Note *n)
 {
 	n->wakeup = 0;
 }

 void
 notesleep(Note *n)
 {
 	if(n->sema.k == 0)
 		initsema(&n->sema.k);
 	while(!n->wakeup)
 		usemacquire(&n->sema);
 }

 void
 notewakeup(Note *n)
 {
 	if(n->sema.k == 0)
 		initsema(&n->sema.k);
 	n->wakeup = 1;
 	usemrelease(&n->sema);
 }


 // BSD interface for threading.
 void
 osinit(void)
 {
 	// Register our thread-creation callback (see {amd64,386}/sys.s).
 	bsdthread_register();
 }

 void
 newosproc(M *m, G *g, void *stk, void (*fn)(void))
 {
 	m->tls[0] = m->id;	// so 386 asm can find it

 	if(0){
 		printf("newosproc stk=%p m=%p g=%p fn=%p id=%d/%d ostk=%p\n",
 			stk, m, g, fn, m->id, m->tls[0], &m);
 	}
 	bsdthread_create(stk, m, g, fn);
 }

 // Called to initialize a new m (including the bootstrap m).
 void
 minit(void)
 {
 	// Initialize signal handling.
 	m->gsignal = malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	signalstack(m->gsignal->stackguard, 32*1024);
 }

 // Mach IPC, to get at semaphores
 // Definitions are in /usr/include/mach on a Mac.

 static void
 macherror(int32 r, int8 *fn)
 {
 	printf("mach error %s: %d\n", fn, r);
 	throw("mach error");
 }

 enum
 {
 	DebugMach = 0
 };

 static MachNDR zerondr;

 #define MACH_MSGH_BITS(a, b) ((a) | ((b)<<8))

 static int32
 mach_msg(MachHeader *h,
 	int32 op,
 	uint32 send_size,
 	uint32 rcv_size,
 	uint32 rcv_name,
 	uint32 timeout,
 	uint32 notify)
 {
 	// TODO: Loop on interrupt.
 	return mach_msg_trap(h, op, send_size, rcv_size, rcv_name, timeout, notify);
 }

 // Mach RPC (MIG)

 enum
 {
 	MinMachMsg = 48,
 	Reply = 100,
 };

 #pragma pack on
 typedef struct CodeMsg CodeMsg;
 struct CodeMsg
 {
 	MachHeader h;
 	MachNDR NDR;
 	int32 code;
 };
 #pragma pack off

 static int32
 machcall(MachHeader *h, int32 maxsize, int32 rxsize)
 {
 	uint32 *p;
 	int32 i, ret, id;
 	uint32 port;
 	CodeMsg *c;

 	if((port = m->machport) == 0){
 		port = mach_reply_port();
 		m->machport = port;
 	}

 	h->msgh_bits |= MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND, MACH_MSG_TYPE_MAKE_SEND_ONCE);
 	h->msgh_local_port = port;
 	h->msgh_reserved = 0;
 	id = h->msgh_id;

 	if(DebugMach){
 		p = (uint32*)h;
 		prints("send:\t");
 		for(i=0; i<h->msgh_size/sizeof(p[0]); i++){
 			prints(" ");
 			sys·printpointer((void*)p[i]);
 			if(i%8 == 7)
 				prints("\n\t");
 		}
 		if(i%8)
 			prints("\n");
 	}

 	ret = mach_msg(h, MACH_SEND_MSG|MACH_RCV_MSG,
 		h->msgh_size, maxsize, port, 0, 0);
 	if(ret != 0){
 		if(DebugMach){
 			prints("mach_msg error ");
 			sys·printint(ret);
 			prints("\n");
 		}
 		return ret;
 	}

 	if(DebugMach){
 		p = (uint32*)h;
 		prints("recv:\t");
 		for(i=0; i<h->msgh_size/sizeof(p[0]); i++){
 			prints(" ");
 			sys·printpointer((void*)p[i]);
 			if(i%8 == 7)
 				prints("\n\t");
 		}
 		if(i%8)
 			prints("\n");
 	}

 	if(h->msgh_id != id+Reply){
 		if(DebugMach){
 			prints("mach_msg reply id mismatch ");
 			sys·printint(h->msgh_id);
 			prints(" != ");
 			sys·printint(id+Reply);
 			prints("\n");
 		}
 		return -303;	// MIG_REPLY_MISMATCH
 	}

 	// Look for a response giving the return value.
 	// Any call can send this back with an error,
 	// and some calls only have return values so they
 	// send it back on success too.  I don't quite see how
 	// you know it's one of these and not the full response
 	// format, so just look if the message is right.
 	c = (CodeMsg*)h;
 	if(h->msgh_size == sizeof(CodeMsg)
 	&& !(h->msgh_bits & MACH_MSGH_BITS_COMPLEX)){
 		if(DebugMach){
 			prints("mig result ");
 			sys·printint(c->code);
 			prints("\n");
 		}
 		return c->code;
 	}

 	if(h->msgh_size != rxsize){
 		if(DebugMach){
 			prints("mach_msg reply size mismatch ");
 			sys·printint(h->msgh_size);
 			prints(" != ");
 			sys·printint(rxsize);
 			prints("\n");
 		}
 		return -307;	// MIG_ARRAY_TOO_LARGE
 	}

 	return 0;
 }


 // Semaphores!

 enum
 {
 	Tmach_semcreate = 3418,
 	Rmach_semcreate = Tmach_semcreate + Reply,

 	Tmach_semdestroy = 3419,
 	Rmach_semdestroy = Tmach_semdestroy + Reply,

 	// Mach calls that get interrupted by Unix signals
 	// return this error code.  We retry them.
 	KERN_ABORTED = 14,
 };

 typedef struct Tmach_semcreateMsg Tmach_semcreateMsg;
 typedef struct Rmach_semcreateMsg Rmach_semcreateMsg;
 typedef struct Tmach_semdestroyMsg Tmach_semdestroyMsg;
 // Rmach_semdestroyMsg = CodeMsg

 #pragma pack on
 struct Tmach_semcreateMsg
 {
 	MachHeader h;
 	MachNDR ndr;
 	int32 policy;
 	int32 value;
 };

 struct Rmach_semcreateMsg
 {
 	MachHeader h;
 	MachBody body;
 	MachPort semaphore;
 };

 struct Tmach_semdestroyMsg
 {
 	MachHeader h;
 	MachBody body;
 	MachPort semaphore;
 };
 #pragma pack off

 uint32
 mach_semcreate(void)
 {
 	union {
 		Tmach_semcreateMsg tx;
 		Rmach_semcreateMsg rx;
 		uint8 pad[MinMachMsg];
 	} m;
 	int32 r;

 	m.tx.h.msgh_bits = 0;
 	m.tx.h.msgh_size = sizeof(m.tx);
 	m.tx.h.msgh_remote_port = mach_task_self();
 	m.tx.h.msgh_id = Tmach_semcreate;
 	m.tx.ndr = zerondr;

 	m.tx.policy = 0;	// 0 = SYNC_POLICY_FIFO
 	m.tx.value = 0;

 	while((r = machcall(&m.tx.h, sizeof m, sizeof(m.rx))) != 0){
 		if(r == KERN_ABORTED)	// interrupted
 			continue;
 		macherror(r, "semaphore_create");
 	}
 	if(m.rx.body.msgh_descriptor_count != 1)
 		unimplemented("mach_semcreate desc count");
 	return m.rx.semaphore.name;
 }

 void
 mach_semdestroy(uint32 sem)
 {
 	union {
 		Tmach_semdestroyMsg tx;
 		uint8 pad[MinMachMsg];
 	} m;
 	int32 r;

 	m.tx.h.msgh_bits = MACH_MSGH_BITS_COMPLEX;
 	m.tx.h.msgh_size = sizeof(m.tx);
 	m.tx.h.msgh_remote_port = mach_task_self();
 	m.tx.h.msgh_id = Tmach_semdestroy;
 	m.tx.body.msgh_descriptor_count = 1;
 	m.tx.semaphore.name = sem;
 	m.tx.semaphore.disposition = MACH_MSG_TYPE_MOVE_SEND;
 	m.tx.semaphore.type = 0;

 	while((r = machcall(&m.tx.h, sizeof m, 0)) != 0){
 		macherror(r, "semaphore_destroy");
 	}
 }

 // The other calls have simple system call traps in sys.s
 int32 mach_semaphore_wait(uint32 sema);
 int32 mach_semaphore_timedwait(uint32 sema, uint32 sec, uint32 nsec);
 int32 mach_semaphore_signal(uint32 sema);
 int32 mach_semaphore_signal_all(uint32 sema);

 void
 mach_semacquire(uint32 sem)
 {
 	int32 r;

 	while((r = mach_semaphore_wait(sem)) != 0) {
 		if(r == KERN_ABORTED)	// interrupted
 			continue;
 		macherror(r, "semaphore_wait");
 	}
 }

 void
 mach_semrelease(uint32 sem)
 {
 	int32 r;

 	while((r = mach_semaphore_signal(sem)) != 0) {
 		if(r == KERN_ABORTED)	// interrupted
 			continue;
 		macherror(r, "semaphore_signal");
 	}
 }
	// Copyright 2009 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.

	#include "runtime.h"
	#include "defs.h"
	#include "os.h"

	static void
	unimplemented(int8 *name)
	{
	prints(name);
	prints(" not implemented\n");
	(int32)1231 = 1231;
	}

	// Thread-safe allocation of a semaphore.
	// Psema points at a kernel semaphore key.
	// It starts out zero, meaning no semaphore.
	// Fill it in, being careful of others calling initsema
	// simultaneously.
	static void
	initsema(uint32 *psema)
	{
	uint32 sema;

	if(*psema != 0) // already have one
	return;

	sema = mach_semcreate();
	if(!cas(psema, 0, sema)){
	// Someone else filled it in. Use theirs.
	mach_semdestroy(sema);
	return;
	}
	}


	// Atomic add and return new value.
	static uint32
	xadd(uint32 volatile *val, int32 delta)
	{
	uint32 oval, nval;

	for(;;){
	oval = *val;
	nval = oval + delta;
	if(cas(val, oval, nval))
	return nval;
	}
	}


	// Blocking locks.

	// Implement Locks, using semaphores.
	// l->key is the number of threads who want the lock.
	// In a race, one thread increments l->key from 0 to 1
	// and the others increment it from >0 to >1. The thread
	// who does the 0->1 increment gets the lock, and the
	// others wait on the semaphore. When the 0->1 thread
	// releases the lock by decrementing l->key, l->key will
	// be >0, so it will increment the semaphore to wake up
	// one of the others. This is the same algorithm used
	// in Plan 9's user-level locks.
	//
	// Note that semaphores are never destroyed (the kernel
	// will clean up when the process exits). We assume for now
	// that Locks are only used for long-lived structures like M and G.

	void
	lock(Lock *l)
	{
	if(m->locks < 0)
	throw("lock count");
	m->locks++;

	// Allocate semaphore if needed.
	if(l->sema == 0)
	initsema(&l->sema);

	if(xadd(&l->key, 1) > 1) // someone else has it; wait
	mach_semacquire(l->sema);
	}

	void
	unlock(Lock *l)
	{
	m->locks--;
	if(m->locks < 0)
	throw("lock count");

	if(xadd(&l->key, -1) > 0) // someone else is waiting
	mach_semrelease(l->sema);
	}


	// User-level semaphore implementation:
	// try to do the operations in user space on u,
	// but when it's time to block, fall back on the kernel semaphore k.
	// This is the same algorithm used in Plan 9.
	void
	usemacquire(Usema *s)
	{
	if((int32)xadd(&s->u, -1) < 0)
	mach_semacquire(s->k);
	}

	void
	usemrelease(Usema *s)
	{
	if((int32)xadd(&s->u, 1) <= 0)
	mach_semrelease(s->k);
	}


	// Event notifications.
	void
	noteclear(Note *n)
	{
	n->wakeup = 0;
	}

	void
	notesleep(Note *n)
	{
	if(n->sema.k == 0)
	initsema(&n->sema.k);
	while(!n->wakeup)
	usemacquire(&n->sema);
	}

	void
	notewakeup(Note *n)
	{
	if(n->sema.k == 0)
	initsema(&n->sema.k);
	n->wakeup = 1;
	usemrelease(&n->sema);
	}


	// BSD interface for threading.
	void
	osinit(void)
	{
	// Register our thread-creation callback (see {amd64,386}/sys.s).
	bsdthread_register();
	}

	void
	newosproc(M m, G g, void stk, void (fn)(void))
	{
	m->tls[0] = m->id; // so 386 asm can find it

	if(0){
	printf("newosproc stk=%p m=%p g=%p fn=%p id=%d/%d ostk=%p\n",
	stk, m, g, fn, m->id, m->tls[0], &m);
	}
	bsdthread_create(stk, m, g, fn);
	}

	// Called to initialize a new m (including the bootstrap m).
	void
	minit(void)
	{
	// Initialize signal handling.
	m->gsignal = malg(32*1024); // OS X wants >=8K, Linux >=2K
	signalstack(m->gsignal->stackguard, 32*1024);
	}

	// Mach IPC, to get at semaphores
	// Definitions are in /usr/include/mach on a Mac.

	static void
	macherror(int32 r, int8 *fn)
	{
	printf("mach error %s: %d\n", fn, r);
	throw("mach error");
	}

	enum
	{
	DebugMach = 0
	};

	static MachNDR zerondr;

	#define MACH_MSGH_BITS(a, b) ((a) \| ((b)<<8))

	static int32
	mach_msg(MachHeader *h,
	int32 op,
	uint32 send_size,
	uint32 rcv_size,
	uint32 rcv_name,
	uint32 timeout,
	uint32 notify)
	{
	// TODO: Loop on interrupt.
	return mach_msg_trap(h, op, send_size, rcv_size, rcv_name, timeout, notify);
	}

	// Mach RPC (MIG)

	enum
	{
	MinMachMsg = 48,
	Reply = 100,
	};

	#pragma pack on
	typedef struct CodeMsg CodeMsg;
	struct CodeMsg
	{
	MachHeader h;
	MachNDR NDR;
	int32 code;
	};
	#pragma pack off

	static int32
	machcall(MachHeader *h, int32 maxsize, int32 rxsize)
	{
	uint32 *p;
	int32 i, ret, id;
	uint32 port;
	CodeMsg *c;

	if((port = m->machport) == 0){
	port = mach_reply_port();
	m->machport = port;
	}

	h->msgh_bits \|= MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND, MACH_MSG_TYPE_MAKE_SEND_ONCE);
	h->msgh_local_port = port;
	h->msgh_reserved = 0;
	id = h->msgh_id;

	if(DebugMach){
	p = (uint32*)h;
	prints("send:\t");
	for(i=0; i<h->msgh_size/sizeof(p[0]); i++){
	prints(" ");
	sys·printpointer((void*)p[i]);
	if(i%8 == 7)
	prints("\n\t");
	}
	if(i%8)
	prints("\n");
	}

	ret = mach_msg(h, MACH_SEND_MSG\|MACH_RCV_MSG,
	h->msgh_size, maxsize, port, 0, 0);
	if(ret != 0){
	if(DebugMach){
	prints("mach_msg error ");
	sys·printint(ret);
	prints("\n");
	}
	return ret;
	}

	if(DebugMach){
	p = (uint32*)h;
	prints("recv:\t");
	for(i=0; i<h->msgh_size/sizeof(p[0]); i++){
	prints(" ");
	sys·printpointer((void*)p[i]);
	if(i%8 == 7)
	prints("\n\t");
	}
	if(i%8)
	prints("\n");
	}

	if(h->msgh_id != id+Reply){
	if(DebugMach){
	prints("mach_msg reply id mismatch ");
	sys·printint(h->msgh_id);
	prints(" != ");
	sys·printint(id+Reply);
	prints("\n");
	}
	return -303; // MIG_REPLY_MISMATCH
	}

	// Look for a response giving the return value.
	// Any call can send this back with an error,
	// and some calls only have return values so they
	// send it back on success too. I don't quite see how
	// you know it's one of these and not the full response
	// format, so just look if the message is right.
	c = (CodeMsg*)h;
	if(h->msgh_size == sizeof(CodeMsg)
	&& !(h->msgh_bits & MACH_MSGH_BITS_COMPLEX)){
	if(DebugMach){
	prints("mig result ");
	sys·printint(c->code);
	prints("\n");
	}
	return c->code;
	}

	if(h->msgh_size != rxsize){
	if(DebugMach){
	prints("mach_msg reply size mismatch ");
	sys·printint(h->msgh_size);
	prints(" != ");
	sys·printint(rxsize);
	prints("\n");
	}
	return -307; // MIG_ARRAY_TOO_LARGE
	}

	return 0;
	}


	// Semaphores!

	enum
	{
	Tmach_semcreate = 3418,
	Rmach_semcreate = Tmach_semcreate + Reply,

	Tmach_semdestroy = 3419,
	Rmach_semdestroy = Tmach_semdestroy + Reply,

	// Mach calls that get interrupted by Unix signals
	// return this error code. We retry them.
	KERN_ABORTED = 14,
	};

	typedef struct Tmach_semcreateMsg Tmach_semcreateMsg;
	typedef struct Rmach_semcreateMsg Rmach_semcreateMsg;
	typedef struct Tmach_semdestroyMsg Tmach_semdestroyMsg;
	// Rmach_semdestroyMsg = CodeMsg

	#pragma pack on
	struct Tmach_semcreateMsg
	{
	MachHeader h;
	MachNDR ndr;
	int32 policy;
	int32 value;
	};

	struct Rmach_semcreateMsg
	{
	MachHeader h;
	MachBody body;
	MachPort semaphore;
	};

	struct Tmach_semdestroyMsg
	{
	MachHeader h;
	MachBody body;
	MachPort semaphore;
	};
	#pragma pack off

	uint32
	mach_semcreate(void)
	{
	union {
	Tmach_semcreateMsg tx;
	Rmach_semcreateMsg rx;
	uint8 pad[MinMachMsg];
	} m;
	int32 r;

	m.tx.h.msgh_bits = 0;
	m.tx.h.msgh_size = sizeof(m.tx);
	m.tx.h.msgh_remote_port = mach_task_self();
	m.tx.h.msgh_id = Tmach_semcreate;
	m.tx.ndr = zerondr;

	m.tx.policy = 0; // 0 = SYNC_POLICY_FIFO
	m.tx.value = 0;

	while((r = machcall(&m.tx.h, sizeof m, sizeof(m.rx))) != 0){
	if(r == KERN_ABORTED) // interrupted
	continue;
	macherror(r, "semaphore_create");
	}
	if(m.rx.body.msgh_descriptor_count != 1)
	unimplemented("mach_semcreate desc count");
	return m.rx.semaphore.name;
	}

	void
	mach_semdestroy(uint32 sem)
	{
	union {
	Tmach_semdestroyMsg tx;
	uint8 pad[MinMachMsg];
	} m;
	int32 r;

	m.tx.h.msgh_bits = MACH_MSGH_BITS_COMPLEX;
	m.tx.h.msgh_size = sizeof(m.tx);
	m.tx.h.msgh_remote_port = mach_task_self();
	m.tx.h.msgh_id = Tmach_semdestroy;
	m.tx.body.msgh_descriptor_count = 1;
	m.tx.semaphore.name = sem;
	m.tx.semaphore.disposition = MACH_MSG_TYPE_MOVE_SEND;
	m.tx.semaphore.type = 0;

	while((r = machcall(&m.tx.h, sizeof m, 0)) != 0){
	macherror(r, "semaphore_destroy");
	}
	}

	// The other calls have simple system call traps in sys.s
	int32 mach_semaphore_wait(uint32 sema);
	int32 mach_semaphore_timedwait(uint32 sema, uint32 sec, uint32 nsec);
	int32 mach_semaphore_signal(uint32 sema);
	int32 mach_semaphore_signal_all(uint32 sema);

	void
	mach_semacquire(uint32 sem)
	{
	int32 r;

	while((r = mach_semaphore_wait(sem)) != 0) {
	if(r == KERN_ABORTED) // interrupted
	continue;
	macherror(r, "semaphore_wait");
	}
	}

	void
	mach_semrelease(uint32 sem)
	{
	int32 r;

	while((r = mach_semaphore_signal(sem)) != 0) {
	if(r == KERN_ABORTED) // interrupted
	continue;
	macherror(r, "semaphore_signal");
	}
	}