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cosmopolitan/libc/thread/pthread_create.c
Justine Tunney a15958edc6
Remove some legacy cruft 
Function trace logs will report stack usage accurately. It won't include
the argv/environ block. Our clone() polyfill is now simpler and does not
use as much stack memory. Function call tracing on x86 is now faster too
2025-01-02 18:44:07 -08:00

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/calls/sig.internal.h"
#include "libc/calls/struct/sigaltstack.h"
#include "libc/calls/struct/sigset.h"
#include "libc/calls/struct/sigset.internal.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/cosmo.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/fmt/itoa.h"
#include "libc/intrin/bsr.h"
#include "libc/intrin/describeflags.h"
#include "libc/intrin/dll.h"
#include "libc/intrin/kprintf.h"
#include "libc/intrin/stack.h"
#include "libc/intrin/strace.h"
#include "libc/intrin/weaken.h"
#include "libc/log/internal.h"
#include "libc/macros.h"
#include "libc/mem/alloca.h"
#include "libc/mem/mem.h"
#include "libc/nexgen32e/crc32.h"
#include "libc/nt/enum/memflags.h"
#include "libc/nt/enum/pageflags.h"
#include "libc/nt/memory.h"
#include "libc/nt/runtime.h"
#include "libc/nt/synchronization.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/stack.h"
#include "libc/runtime/syslib.internal.h"
#include "libc/str/locale.internal.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/auxv.h"
#include "libc/sysv/consts/clone.h"
#include "libc/sysv/consts/prot.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/consts/ss.h"
#include "libc/thread/posixthread.internal.h"
#include "libc/thread/thread.h"
#include "libc/thread/tls.h"
#include "third_party/nsync/wait_s.internal.h"
__static_yoink("nsync_mu_lock");
__static_yoink("nsync_mu_unlock");
__static_yoink("nsync_mu_trylock");
__static_yoink("nsync_mu_rlock");
__static_yoink("nsync_mu_runlock");
__static_yoink("_pthread_onfork_prepare");
__static_yoink("_pthread_onfork_parent");
__static_yoink("_pthread_onfork_child");
void _pthread_free(struct PosixThread *pt) {
// thread must be removed from _pthread_list before calling
unassert(dll_is_alone(&pt->list) && &pt->list != _pthread_list);
// do nothing for the one and only magical statical posix thread
if (pt->pt_flags & PT_STATIC)
return;
// unmap stack if the cosmo runtime was responsible for mapping it
if (pt->pt_flags & PT_OWNSTACK)
cosmo_stack_free(pt->pt_attr.__stackaddr, pt->pt_attr.__stacksize,
pt->pt_attr.__guardsize);
// reclaim thread's cached nsync waiter object
if (pt->tib->tib_nsync)
nsync_waiter_destroy_(pt->tib->tib_nsync);
// free any additional upstream system resources
// our fork implementation wipes this handle in child automatically
uint64_t syshand =
atomic_load_explicit(&pt->tib->tib_syshand, memory_order_relaxed);
if (syshand) {
if (IsWindows())
unassert(CloseHandle(syshand)); // non-inheritable
else if (IsXnuSilicon())
unassert(!__syslib->__pthread_join(syshand, 0));
}
// free heap memory associated with thread
bulk_free(
(void *[]){
pt->pt_flags & PT_OWNSIGALTSTACK ? pt->pt_attr.__sigaltstackaddr : 0,
pt->pt_tls,
pt,
},
3);
}
void _pthread_decimate(enum PosixThreadStatus threshold) {
struct PosixThread *pt;
struct Dll *e, *e2, *list = 0;
enum PosixThreadStatus status;
// acquire posix threads gil
_pthread_lock();
// swiftly remove every single zombie
// that isn't being held by a killing thread
for (e = dll_last(_pthread_list); e; e = e2) {
e2 = dll_prev(_pthread_list, e);
pt = POSIXTHREAD_CONTAINER(e);
if (atomic_load_explicit(&pt->pt_refs, memory_order_acquire) > 0)
continue; // pthread_kill() has a lease on this thread
if (atomic_load_explicit(&pt->tib->tib_ctid, memory_order_acquire))
continue; // thread is still using stack so leave alone
status = atomic_load_explicit(&pt->pt_status, memory_order_acquire);
if (status < threshold) {
if (threshold == kPosixThreadZombie)
break; // zombies only exist at the end of the linked list
continue;
}
if (status == kPosixThreadTerminated)
if (!(pt->pt_flags & PT_STATIC))
STRACE("warning: you forgot to join or detach thread id %d",
atomic_load_explicit(&pt->tib->tib_ptid, memory_order_acquire));
dll_remove(&_pthread_list, e);
dll_make_first(&list, e);
}
// release posix threads gil
_pthread_unlock();
// now free our thread local batch of zombies
// because death is a release and not a punishment
// this is advantaged by not holding locks over munmap
while ((e = dll_first(list))) {
pt = POSIXTHREAD_CONTAINER(e);
dll_remove(&list, e);
_pthread_free(pt);
}
}
static int PosixThread(void *arg) {
struct PosixThread *pt = arg;
// setup scheduling
if (pt->pt_attr.__inheritsched == PTHREAD_EXPLICIT_SCHED) {
unassert(_weaken(_pthread_reschedule));
_weaken(_pthread_reschedule)(pt); // yoinked by attribute builder
}
// setup signal stack
if (pt->pt_attr.__sigaltstacksize) {
struct sigaltstack *ss = alloca(sizeof(struct sigaltstack));
ss->ss_sp = pt->pt_attr.__sigaltstackaddr;
ss->ss_size = pt->pt_attr.__sigaltstacksize;
ss->ss_flags = 0;
unassert(!sigaltstack(ss, 0));
}
// set long jump handler so pthread_exit can bring control back here
if (!__builtin_setjmp(pt->pt_exiter)) {
// setup signals for new thread
pt->pt_attr.__sigmask &= ~(1ull << (SIGTHR - 1));
if (IsWindows() || IsMetal()) {
atomic_store_explicit(&__get_tls()->tib_sigmask, pt->pt_attr.__sigmask,
memory_order_release);
if (_weaken(__sig_check))
_weaken(__sig_check)();
} else {
sys_sigprocmask(SIG_SETMASK, &pt->pt_attr.__sigmask, 0);
}
void *ret = pt->pt_start(pt->pt_val);
// ensure pthread_cleanup_pop(), and pthread_exit() popped cleanup
unassert(!pt->pt_cleanup);
// calling pthread_exit() will either jump back here, or call exit
pthread_exit(ret);
}
// avoid signal handler being triggered after we trash our own stack
__sig_block();
// return to clone polyfill which clears tid, wakes futex, and exits
return 0;
}
static errno_t pthread_create_impl(pthread_t *thread,
const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg,
sigset_t oldsigs) {
int rc, e = errno;
struct PosixThread *pt;
// create posix thread object
if (!(pt = calloc(1, sizeof(struct PosixThread)))) {
errno = e;
return EAGAIN;
}
dll_init(&pt->list);
pt->pt_locale = &__global_locale;
pt->pt_start = start_routine;
pt->pt_val = arg;
// create thread local storage memory
if (!(pt->pt_tls = _mktls(&pt->tib))) {
free(pt);
errno = e;
return EAGAIN;
}
// setup attributes
if (attr) {
pt->pt_attr = *attr;
attr = 0;
} else {
pthread_attr_init(&pt->pt_attr);
}
// setup stack
if (pt->pt_attr.__stackaddr) {
// caller supplied their own stack
// assume they know what they're doing as much as possible
if (IsOpenbsd()) {
if ((rc = FixupCustomStackOnOpenbsd(&pt->pt_attr))) {
_pthread_free(pt);
return rc;
}
}
} else {
// cosmo is managing the stack
pt->pt_flags |= PT_OWNSTACK;
errno_t err =
cosmo_stack_alloc(&pt->pt_attr.__stacksize, &pt->pt_attr.__guardsize,
&pt->pt_attr.__stackaddr);
if (err) {
_pthread_free(pt);
if (err == EINVAL || err == EOVERFLOW) {
return EINVAL;
} else {
return EAGAIN;
}
}
}
// setup signal stack
if (pt->pt_attr.__sigaltstacksize) {
if (!pt->pt_attr.__sigaltstackaddr) {
if (!(pt->pt_attr.__sigaltstackaddr =
malloc(pt->pt_attr.__sigaltstacksize))) {
_pthread_free(pt);
return errno;
}
pt->pt_flags |= PT_OWNSIGALTSTACK;
}
}
// set initial status
pt->tib->tib_pthread = (pthread_t)pt;
atomic_store_explicit(&pt->tib->tib_sigmask, -1, memory_order_relaxed);
if (!pt->pt_attr.__havesigmask) {
pt->pt_attr.__havesigmask = true;
pt->pt_attr.__sigmask = oldsigs;
}
switch (pt->pt_attr.__detachstate) {
case PTHREAD_CREATE_JOINABLE:
atomic_store_explicit(&pt->pt_status, kPosixThreadJoinable,
memory_order_relaxed);
break;
case PTHREAD_CREATE_DETACHED:
atomic_store_explicit(&pt->pt_status, kPosixThreadDetached,
memory_order_relaxed);
break;
default:
_pthread_free(pt);
return EINVAL;
}
// add thread to global list
// we add it to the beginning since zombies go at the end
_pthread_lock();
dll_make_first(&_pthread_list, &pt->list);
_pthread_unlock();
// if pthread_attr_setdetachstate() was used then it's possible for
// the `pt` object to be freed before this clone call has returned!
_pthread_ref(pt);
// launch PosixThread(pt) in new thread
if ((rc = clone(
PosixThread, pt->pt_attr.__stackaddr, pt->pt_attr.__stacksize,
CLONE_VM | CLONE_THREAD | CLONE_FS | CLONE_FILES | CLONE_SIGHAND |
CLONE_SYSVSEM | CLONE_SETTLS | CLONE_PARENT_SETTID |
CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID,
pt, &pt->tib->tib_ptid, __adj_tls(pt->tib), &pt->tib->tib_ctid))) {
_pthread_lock();
dll_remove(&_pthread_list, &pt->list);
_pthread_unlock();
_pthread_free(pt);
return rc;
}
*thread = (pthread_t)pt;
return 0;
}
static const char *DescribeHandle(char buf[12], errno_t err, pthread_t *th) {
if (err)
return "n/a";
if (!th)
return "NULL";
FormatInt32(buf, _pthread_tid((struct PosixThread *)*th));
return buf;
}
/**
* Creates thread, e.g.
*
* void *worker(void *arg) {
* fputs(arg, stdout);
* return "there\n";
* }
*
* int main() {
* void *result;
* pthread_t id;
* pthread_create(&id, 0, worker, "hi ");
* pthread_join(id, &result);
* fputs(result, stdout);
* }
*
* Here's the OSI model of threads in Cosmopolitan:
*
* ┌──────────────────┐
* │ pthread_create() │ - Standard
* └─────────┬────────┘ Abstraction
* ┌─────────┴────────┐
* │ clone() │ - Polyfill
* └─────────┬────────┘
* ┌────────┬──┴┬─┬─┬─────────┐ - Kernel
* ┌─────┴─────┐ │ │ │┌┴──────┐ │ Interfaces
* │ sys_clone │ │ │ ││ tfork │ ┌┴─────────────┐
* └───────────┘ │ │ │└───────┘ │ CreateThread │
* ┌───────────────┴──┐│┌┴────────┐ └──────────────┘
* │ bsdthread_create │││ thr_new │
* └──────────────────┘│└─────────┘
* ┌───────┴──────┐
* │ _lwp_create │
* └──────────────┘
*
* @param thread is used to output the thread id upon success, which
* must be non-null
* @param attr points to launch configuration, or may be null
* to use sensible defaults; it must be initialized using
* pthread_attr_init()
* @param start_routine is your thread's callback function
* @param arg is an arbitrary value passed to `start_routine`
* @return 0 on success, or errno on error
* @raise EAGAIN if resources to create thread weren't available
* @raise EINVAL if `attr` was supplied and had unnaceptable data
* @raise EPERM if scheduling policy was requested and user account
* isn't authorized to use it
* @returnserrno
*/
errno_t pthread_create(pthread_t *thread, const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg) {
errno_t err;
_pthread_decimate(kPosixThreadZombie);
BLOCK_SIGNALS;
err = pthread_create_impl(thread, attr, start_routine, arg, _SigMask);
ALLOW_SIGNALS;
STRACE("pthread_create([%s], %p, %t, %p) → %s",
DescribeHandle(alloca(12), err, thread), attr, start_routine, arg,
DescribeErrno(err));
if (!err)
_pthread_unref(*(struct PosixThread **)thread);
return err;
}
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