src/pkg/runtime/linux/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"
 #include "stack.h"

 extern SigTab runtime·sigtab[];
 static int32 proccount;

 int32 runtime·open(uint8*, int32, int32);
 int32 runtime·close(int32);
 int32 runtime·read(int32, void*, int32);

 // Linux futex.
 //
 //	futexsleep(uint32 *addr, uint32 val)
 //	futexwakeup(uint32 *addr)
 //
 // Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
 // Futexwakeup wakes up threads sleeping on addr.
 // Futexsleep is allowed to wake up spuriously.

 enum
 {
 	MUTEX_UNLOCKED = 0,
 	MUTEX_LOCKED = 1,
 	MUTEX_SLEEPING = 2,

 	ACTIVE_SPIN = 4,
 	ACTIVE_SPIN_CNT = 30,
 	PASSIVE_SPIN = 1,

 	FUTEX_WAIT = 0,
 	FUTEX_WAKE = 1,

 	EINTR = 4,
 	EAGAIN = 11,
 };

 // TODO(rsc): I tried using 1<<40 here but futex woke up (-ETIMEDOUT).
 // I wonder if the timespec that gets to the kernel
 // actually has two 32-bit numbers in it, so that
 // a 64-bit 1<<40 ends up being 0 seconds,
 // 1<<8 nanoseconds.
 static Timespec longtime =
 {
 	1<<30,	// 34 years
 	0
 };

 // Atomically,
 //	if(*addr == val) sleep
 // Might be woken up spuriously; that's allowed.
 static void
 futexsleep(uint32 *addr, uint32 val)
 {
 	// Some Linux kernels have a bug where futex of
 	// FUTEX_WAIT returns an internal error code
 	// as an errno.  Libpthread ignores the return value
 	// here, and so can we: as it says a few lines up,
 	// spurious wakeups are allowed.
 	runtime·futex(addr, FUTEX_WAIT, val, &longtime, nil, 0);
 }

 // If any procs are sleeping on addr, wake up at most cnt.
 static void
 futexwakeup(uint32 *addr, uint32 cnt)
 {
 	int64 ret;

 	ret = runtime·futex(addr, FUTEX_WAKE, cnt, nil, nil, 0);

 	if(ret >= 0)
 		return;

 	// I don't know that futex wakeup can return
 	// EAGAIN or EINTR, but if it does, it would be
 	// safe to loop and call futex again.
 	runtime·printf("futexwakeup addr=%p returned %D\n", addr, ret);
 	*(int32*)0x1006 = 0x1006;
 }

 static int32
 getproccount(void)
 {
 	int32 fd, rd, cnt, cpustrlen;
 	byte *cpustr, *pos, *bufpos;
 	byte buf[256];

 	fd = runtime·open((byte*)"/proc/stat", O_RDONLY|O_CLOEXEC, 0);
 	if(fd == -1)
 		return 1;
 	cnt = 0;
 	bufpos = buf;
 	cpustr = (byte*)"\ncpu";
 	cpustrlen = runtime·findnull(cpustr);
 	for(;;) {
 		rd = runtime·read(fd, bufpos, sizeof(buf)-cpustrlen);
 		if(rd == -1)
 			break;
 		bufpos[rd] = 0;
 		for(pos=buf; pos=runtime·strstr(pos, cpustr); cnt++, pos++) {
 		}
 		if(rd < cpustrlen)
 			break;
 		runtime·memmove(buf, bufpos+rd-cpustrlen+1, cpustrlen-1);
 		bufpos = buf+cpustrlen-1;
 	}
 	runtime·close(fd);
 	return cnt ? cnt : 1;
 }

 // Possible lock states are MUTEX_UNLOCKED, MUTEX_LOCKED and MUTEX_SLEEPING.
 // MUTEX_SLEEPING means that there is presumably at least one sleeping thread.
 // Note that there can be spinning threads during all states - they do not
 // affect mutex's state.
 static void
 futexlock(Lock *l)
 {
 	uint32 i, v, wait, spin;

 	// Speculative grab for lock.
 	v = runtime·xchg(&l->key, MUTEX_LOCKED);
 	if(v == MUTEX_UNLOCKED)
 		return;

 	// wait is either MUTEX_LOCKED or MUTEX_SLEEPING
 	// depending on whether there is a thread sleeping
 	// on this mutex.  If we ever change l->key from
 	// MUTEX_SLEEPING to some other value, we must be
 	// careful to change it back to MUTEX_SLEEPING before
 	// returning, to ensure that the sleeping thread gets
 	// its wakeup call.
 	wait = v;

 	if(proccount == 0)
 		proccount = getproccount();

 	// On uniprocessor's, no point spinning.
 	// On multiprocessors, spin for ACTIVE_SPIN attempts.
 	spin = 0;
 	if(proccount > 1)
 		spin = ACTIVE_SPIN;

 	for(;;) {
 		// Try for lock, spinning.
 		for(i = 0; i < spin; i++) {
 			while(l->key == MUTEX_UNLOCKED)
 				if(runtime·cas(&l->key, MUTEX_UNLOCKED, wait))
 						return;
 			runtime·procyield(ACTIVE_SPIN_CNT);
 		}

 		// Try for lock, rescheduling.
 		for(i=0; i < PASSIVE_SPIN; i++) {
 			while(l->key == MUTEX_UNLOCKED)
 				if(runtime·cas(&l->key, MUTEX_UNLOCKED, wait))
 					return;
 			runtime·osyield();
 		}

 		// Sleep.
 		v = runtime·xchg(&l->key, MUTEX_SLEEPING);
 		if(v == MUTEX_UNLOCKED)
 			return;
 		wait = MUTEX_SLEEPING;
 		futexsleep(&l->key, MUTEX_SLEEPING);
 	}
 }

 static void
 futexunlock(Lock *l)
 {
 	uint32 v;

 	v = runtime·xchg(&l->key, MUTEX_UNLOCKED);
 	if(v == MUTEX_UNLOCKED)
 		runtime·throw("unlock of unlocked lock");
 	if(v == MUTEX_SLEEPING)
 		futexwakeup(&l->key, 1);
 }

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

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


 // One-time notifications.
 void
 runtime·noteclear(Note *n)
 {
 	n->state = 0;
 }

 void
 runtime·notewakeup(Note *n)
 {
 	runtime·xchg(&n->state, 1);
 	futexwakeup(&n->state, 1<<30);
 }

 void
 runtime·notesleep(Note *n)
 {
 	while(runtime·atomicload(&n->state) == 0)
 		futexsleep(&n->state, 0);
 }


 // Clone, the Linux rfork.
 enum
 {
 	CLONE_VM = 0x100,
 	CLONE_FS = 0x200,
 	CLONE_FILES = 0x400,
 	CLONE_SIGHAND = 0x800,
 	CLONE_PTRACE = 0x2000,
 	CLONE_VFORK = 0x4000,
 	CLONE_PARENT = 0x8000,
 	CLONE_THREAD = 0x10000,
 	CLONE_NEWNS = 0x20000,
 	CLONE_SYSVSEM = 0x40000,
 	CLONE_SETTLS = 0x80000,
 	CLONE_PARENT_SETTID = 0x100000,
 	CLONE_CHILD_CLEARTID = 0x200000,
 	CLONE_UNTRACED = 0x800000,
 	CLONE_CHILD_SETTID = 0x1000000,
 	CLONE_STOPPED = 0x2000000,
 	CLONE_NEWUTS = 0x4000000,
 	CLONE_NEWIPC = 0x8000000,
 };

 void
 runtime·newosproc(M *m, G *g, void *stk, void (*fn)(void))
 {
 	int32 ret;
 	int32 flags;

 	/*
 	 * note: strace gets confused if we use CLONE_PTRACE here.
 	 */
 	flags = CLONE_VM	/* share memory */
 		| CLONE_FS	/* share cwd, etc */
 		| CLONE_FILES	/* share fd table */
 		| CLONE_SIGHAND	/* share sig handler table */
 		| CLONE_THREAD	/* revisit - okay for now */
 		;

 	m->tls[0] = m->id;	// so 386 asm can find it
 	if(0){
 		runtime·printf("newosproc stk=%p m=%p g=%p fn=%p clone=%p id=%d/%d ostk=%p\n",
 			stk, m, g, fn, runtime·clone, m->id, m->tls[0], &m);
 	}

 	if((ret = runtime·clone(flags, stk, m, g, fn)) < 0) {
 		runtime·printf("runtime: failed to create new OS thread (have %d already; errno=%d)\n", runtime·mcount(), -ret);
 		runtime·throw("runtime.newosproc");
 	}
 }

 void
 runtime·osinit(void)
 {
 }

 void
 runtime·goenvs(void)
 {
 	runtime·goenvs_unix();
 }

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

 void
 runtime·sigpanic(void)
 {
 	switch(g->sig) {
 	case SIGBUS:
 		if(g->sigcode0 == BUS_ADRERR && g->sigcode1 < 0x1000)
 			runtime·panicstring("invalid memory address or nil pointer dereference");
 		runtime·printf("unexpected fault address %p\n", g->sigcode1);
 		runtime·throw("fault");
 	case SIGSEGV:
 		if((g->sigcode0 == 0 || g->sigcode0 == SEGV_MAPERR || g->sigcode0 == SEGV_ACCERR) && g->sigcode1 < 0x1000)
 			runtime·panicstring("invalid memory address or nil pointer dereference");
 		runtime·printf("unexpected fault address %p\n", g->sigcode1);
 		runtime·throw("fault");
 	case SIGFPE:
 		switch(g->sigcode0) {
 		case FPE_INTDIV:
 			runtime·panicstring("integer divide by zero");
 		case FPE_INTOVF:
 			runtime·panicstring("integer overflow");
 		}
 		runtime·panicstring("floating point error");
 	}
 	runtime·panicstring(runtime·sigtab[g->sig].name);
 }
	// 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"
	#include "stack.h"

	extern SigTab runtime·sigtab[];
	static int32 proccount;

	int32 runtime·open(uint8*, int32, int32);
	int32 runtime·close(int32);
	int32 runtime·read(int32, void*, int32);

	// Linux futex.
	//
	// futexsleep(uint32 *addr, uint32 val)
	// futexwakeup(uint32 *addr)
	//
	// Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
	// Futexwakeup wakes up threads sleeping on addr.
	// Futexsleep is allowed to wake up spuriously.

	enum
	{
	MUTEX_UNLOCKED = 0,
	MUTEX_LOCKED = 1,
	MUTEX_SLEEPING = 2,

	ACTIVE_SPIN = 4,
	ACTIVE_SPIN_CNT = 30,
	PASSIVE_SPIN = 1,

	FUTEX_WAIT = 0,
	FUTEX_WAKE = 1,

	EINTR = 4,
	EAGAIN = 11,
	};

	// TODO(rsc): I tried using 1<<40 here but futex woke up (-ETIMEDOUT).
	// I wonder if the timespec that gets to the kernel
	// actually has two 32-bit numbers in it, so that
	// a 64-bit 1<<40 ends up being 0 seconds,
	// 1<<8 nanoseconds.
	static Timespec longtime =
	{
	1<<30, // 34 years
	0
	};

	// Atomically,
	// if(*addr == val) sleep
	// Might be woken up spuriously; that's allowed.
	static void
	futexsleep(uint32 *addr, uint32 val)
	{
	// Some Linux kernels have a bug where futex of
	// FUTEX_WAIT returns an internal error code
	// as an errno. Libpthread ignores the return value
	// here, and so can we: as it says a few lines up,
	// spurious wakeups are allowed.
	runtime·futex(addr, FUTEX_WAIT, val, &longtime, nil, 0);
	}

	// If any procs are sleeping on addr, wake up at most cnt.
	static void
	futexwakeup(uint32 *addr, uint32 cnt)
	{
	int64 ret;

	ret = runtime·futex(addr, FUTEX_WAKE, cnt, nil, nil, 0);

	if(ret >= 0)
	return;

	// I don't know that futex wakeup can return
	// EAGAIN or EINTR, but if it does, it would be
	// safe to loop and call futex again.
	runtime·printf("futexwakeup addr=%p returned %D\n", addr, ret);
	(int32)0x1006 = 0x1006;
	}

	static int32
	getproccount(void)
	{
	int32 fd, rd, cnt, cpustrlen;
	byte cpustr, pos, *bufpos;
	byte buf[256];

	fd = runtime·open((byte*)"/proc/stat", O_RDONLY\|O_CLOEXEC, 0);
	if(fd == -1)
	return 1;
	cnt = 0;
	bufpos = buf;
	cpustr = (byte*)"\ncpu";
	cpustrlen = runtime·findnull(cpustr);
	for(;;) {
	rd = runtime·read(fd, bufpos, sizeof(buf)-cpustrlen);
	if(rd == -1)
	break;
	bufpos[rd] = 0;
	for(pos=buf; pos=runtime·strstr(pos, cpustr); cnt++, pos++) {
	}
	if(rd < cpustrlen)
	break;
	runtime·memmove(buf, bufpos+rd-cpustrlen+1, cpustrlen-1);
	bufpos = buf+cpustrlen-1;
	}
	runtime·close(fd);
	return cnt ? cnt : 1;
	}

	// Possible lock states are MUTEX_UNLOCKED, MUTEX_LOCKED and MUTEX_SLEEPING.
	// MUTEX_SLEEPING means that there is presumably at least one sleeping thread.
	// Note that there can be spinning threads during all states - they do not
	// affect mutex's state.
	static void
	futexlock(Lock *l)
	{
	uint32 i, v, wait, spin;

	// Speculative grab for lock.
	v = runtime·xchg(&l->key, MUTEX_LOCKED);
	if(v == MUTEX_UNLOCKED)
	return;

	// wait is either MUTEX_LOCKED or MUTEX_SLEEPING
	// depending on whether there is a thread sleeping
	// on this mutex. If we ever change l->key from
	// MUTEX_SLEEPING to some other value, we must be
	// careful to change it back to MUTEX_SLEEPING before
	// returning, to ensure that the sleeping thread gets
	// its wakeup call.
	wait = v;

	if(proccount == 0)
	proccount = getproccount();

	// On uniprocessor's, no point spinning.
	// On multiprocessors, spin for ACTIVE_SPIN attempts.
	spin = 0;
	if(proccount > 1)
	spin = ACTIVE_SPIN;

	for(;;) {
	// Try for lock, spinning.
	for(i = 0; i < spin; i++) {
	while(l->key == MUTEX_UNLOCKED)
	if(runtime·cas(&l->key, MUTEX_UNLOCKED, wait))
	return;
	runtime·procyield(ACTIVE_SPIN_CNT);
	}

	// Try for lock, rescheduling.
	for(i=0; i < PASSIVE_SPIN; i++) {
	while(l->key == MUTEX_UNLOCKED)
	if(runtime·cas(&l->key, MUTEX_UNLOCKED, wait))
	return;
	runtime·osyield();
	}

	// Sleep.
	v = runtime·xchg(&l->key, MUTEX_SLEEPING);
	if(v == MUTEX_UNLOCKED)
	return;
	wait = MUTEX_SLEEPING;
	futexsleep(&l->key, MUTEX_SLEEPING);
	}
	}

	static void
	futexunlock(Lock *l)
	{
	uint32 v;

	v = runtime·xchg(&l->key, MUTEX_UNLOCKED);
	if(v == MUTEX_UNLOCKED)
	runtime·throw("unlock of unlocked lock");
	if(v == MUTEX_SLEEPING)
	futexwakeup(&l->key, 1);
	}

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

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


	// One-time notifications.
	void
	runtime·noteclear(Note *n)
	{
	n->state = 0;
	}

	void
	runtime·notewakeup(Note *n)
	{
	runtime·xchg(&n->state, 1);
	futexwakeup(&n->state, 1<<30);
	}

	void
	runtime·notesleep(Note *n)
	{
	while(runtime·atomicload(&n->state) == 0)
	futexsleep(&n->state, 0);
	}


	// Clone, the Linux rfork.
	enum
	{
	CLONE_VM = 0x100,
	CLONE_FS = 0x200,
	CLONE_FILES = 0x400,
	CLONE_SIGHAND = 0x800,
	CLONE_PTRACE = 0x2000,
	CLONE_VFORK = 0x4000,
	CLONE_PARENT = 0x8000,
	CLONE_THREAD = 0x10000,
	CLONE_NEWNS = 0x20000,
	CLONE_SYSVSEM = 0x40000,
	CLONE_SETTLS = 0x80000,
	CLONE_PARENT_SETTID = 0x100000,
	CLONE_CHILD_CLEARTID = 0x200000,
	CLONE_UNTRACED = 0x800000,
	CLONE_CHILD_SETTID = 0x1000000,
	CLONE_STOPPED = 0x2000000,
	CLONE_NEWUTS = 0x4000000,
	CLONE_NEWIPC = 0x8000000,
	};

	void
	runtime·newosproc(M m, G g, void stk, void (fn)(void))
	{
	int32 ret;
	int32 flags;

	/*
	* note: strace gets confused if we use CLONE_PTRACE here.
	*/
	flags = CLONE_VM /* share memory */
	\| CLONE_FS /* share cwd, etc */
	\| CLONE_FILES /* share fd table */
	\| CLONE_SIGHAND /* share sig handler table */
	\| CLONE_THREAD /* revisit - okay for now */
	;

	m->tls[0] = m->id; // so 386 asm can find it
	if(0){
	runtime·printf("newosproc stk=%p m=%p g=%p fn=%p clone=%p id=%d/%d ostk=%p\n",
	stk, m, g, fn, runtime·clone, m->id, m->tls[0], &m);
	}

	if((ret = runtime·clone(flags, stk, m, g, fn)) < 0) {
	runtime·printf("runtime: failed to create new OS thread (have %d already; errno=%d)\n", runtime·mcount(), -ret);
	runtime·throw("runtime.newosproc");
	}
	}

	void
	runtime·osinit(void)
	{
	}

	void
	runtime·goenvs(void)
	{
	runtime·goenvs_unix();
	}

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

	void
	runtime·sigpanic(void)
	{
	switch(g->sig) {
	case SIGBUS:
	if(g->sigcode0 == BUS_ADRERR && g->sigcode1 < 0x1000)
	runtime·panicstring("invalid memory address or nil pointer dereference");
	runtime·printf("unexpected fault address %p\n", g->sigcode1);
	runtime·throw("fault");
	case SIGSEGV:
	if((g->sigcode0 == 0 \|\| g->sigcode0 == SEGV_MAPERR \|\| g->sigcode0 == SEGV_ACCERR) && g->sigcode1 < 0x1000)
	runtime·panicstring("invalid memory address or nil pointer dereference");
	runtime·printf("unexpected fault address %p\n", g->sigcode1);
	runtime·throw("fault");
	case SIGFPE:
	switch(g->sigcode0) {
	case FPE_INTDIV:
	runtime·panicstring("integer divide by zero");
	case FPE_INTOVF:
	runtime·panicstring("integer overflow");
	}
	runtime·panicstring("floating point error");
	}
	runtime·panicstring(runtime·sigtab[g->sig].name);
	}