--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/src/threadpool.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,419 @@
+/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv-common.h"
+
+#if !defined(_WIN32)
+# include "unix/internal.h"
+#endif
+
+#include <stdlib.h>
+
+#define MAX_THREADPOOL_SIZE 1024
+
+static uv_once_t once = UV_ONCE_INIT;
+static uv_cond_t cond;
+static uv_mutex_t mutex;
+static unsigned int idle_threads;
+static unsigned int slow_io_work_running;
+static unsigned int nthreads;
+static uv_thread_t* threads;
+static uv_thread_t default_threads[4];
+static struct uv__queue exit_message;
+static struct uv__queue wq;
+static struct uv__queue run_slow_work_message;
+static struct uv__queue slow_io_pending_wq;
+
+static unsigned int slow_work_thread_threshold(void) {
+  return (nthreads + 1) / 2;
+}
+
+static void uv__cancelled(struct uv__work* w) {
+  abort();
+}
+
+
+/* To avoid deadlock with uv_cancel() it's crucial that the worker
+ * never holds the global mutex and the loop-local mutex at the same time.
+ */
+static void worker(void* arg) {
+  struct uv__work* w;
+  struct uv__queue* q;
+  int is_slow_work;
+
+  uv_thread_setname("libuv-worker");
+  uv_sem_post((uv_sem_t*) arg);
+  arg = NULL;
+
+  uv_mutex_lock(&mutex);
+  for (;;) {
+    /* `mutex` should always be locked at this point. */
+
+    /* Keep waiting while either no work is present or only slow I/O
+       and we're at the threshold for that. */
+    while (uv__queue_empty(&wq) ||
+           (uv__queue_head(&wq) == &run_slow_work_message &&
+            uv__queue_next(&run_slow_work_message) == &wq &&
+            slow_io_work_running >= slow_work_thread_threshold())) {
+      idle_threads += 1;
+      uv_cond_wait(&cond, &mutex);
+      idle_threads -= 1;
+    }
+
+    q = uv__queue_head(&wq);
+    if (q == &exit_message) {
+      uv_cond_signal(&cond);
+      uv_mutex_unlock(&mutex);
+      break;
+    }
+
+    uv__queue_remove(q);
+    uv__queue_init(q);  /* Signal uv_cancel() that the work req is executing. */
+
+    is_slow_work = 0;
+    if (q == &run_slow_work_message) {
+      /* If we're at the slow I/O threshold, re-schedule until after all
+         other work in the queue is done. */
+      if (slow_io_work_running >= slow_work_thread_threshold()) {
+        uv__queue_insert_tail(&wq, q);
+        continue;
+      }
+
+      /* If we encountered a request to run slow I/O work but there is none
+         to run, that means it's cancelled => Start over. */
+      if (uv__queue_empty(&slow_io_pending_wq))
+        continue;
+
+      is_slow_work = 1;
+      slow_io_work_running++;
+
+      q = uv__queue_head(&slow_io_pending_wq);
+      uv__queue_remove(q);
+      uv__queue_init(q);
+
+      /* If there is more slow I/O work, schedule it to be run as well. */
+      if (!uv__queue_empty(&slow_io_pending_wq)) {
+        uv__queue_insert_tail(&wq, &run_slow_work_message);
+        if (idle_threads > 0)
+          uv_cond_signal(&cond);
+      }
+    }
+
+    uv_mutex_unlock(&mutex);
+
+    w = uv__queue_data(q, struct uv__work, wq);
+    w->work(w);
+
+    uv_mutex_lock(&w->loop->wq_mutex);
+    w->work = NULL;  /* Signal uv_cancel() that the work req is done
+                        executing. */
+    uv__queue_insert_tail(&w->loop->wq, &w->wq);
+    uv_async_send(&w->loop->wq_async);
+    uv_mutex_unlock(&w->loop->wq_mutex);
+
+    /* Lock `mutex` since that is expected at the start of the next
+     * iteration. */
+    uv_mutex_lock(&mutex);
+    if (is_slow_work) {
+      /* `slow_io_work_running` is protected by `mutex`. */
+      slow_io_work_running--;
+    }
+  }
+}
+
+
+static void post(struct uv__queue* q, enum uv__work_kind kind) {
+  uv_mutex_lock(&mutex);
+  if (kind == UV__WORK_SLOW_IO) {
+    /* Insert into a separate queue. */
+    uv__queue_insert_tail(&slow_io_pending_wq, q);
+    if (!uv__queue_empty(&run_slow_work_message)) {
+      /* Running slow I/O tasks is already scheduled => Nothing to do here.
+         The worker that runs said other task will schedule this one as well. */
+      uv_mutex_unlock(&mutex);
+      return;
+    }
+    q = &run_slow_work_message;
+  }
+
+  uv__queue_insert_tail(&wq, q);
+  if (idle_threads > 0)
+    uv_cond_signal(&cond);
+  uv_mutex_unlock(&mutex);
+}
+
+
+#ifdef __MVS__
+/* TODO(itodorov) - zos: revisit when Woz compiler is available. */
+__attribute__((destructor))
+#endif
+void uv__threadpool_cleanup(void) {
+  unsigned int i;
+
+  if (nthreads == 0)
+    return;
+
+#ifndef __MVS__
+  /* TODO(gabylb) - zos: revisit when Woz compiler is available. */
+  post(&exit_message, UV__WORK_CPU);
+#endif
+
+  for (i = 0; i < nthreads; i++)
+    if (uv_thread_join(threads + i))
+      abort();
+
+  if (threads != default_threads)
+    uv__free(threads);
+
+  uv_mutex_destroy(&mutex);
+  uv_cond_destroy(&cond);
+
+  threads = NULL;
+  nthreads = 0;
+}
+
+
+static void init_threads(void) {
+  uv_thread_options_t config;
+  unsigned int i;
+  const char* val;
+  uv_sem_t sem;
+
+  nthreads = ARRAY_SIZE(default_threads);
+  val = getenv("UV_THREADPOOL_SIZE");
+  if (val != NULL)
+    nthreads = atoi(val);
+  if (nthreads == 0)
+    nthreads = 1;
+  if (nthreads > MAX_THREADPOOL_SIZE)
+    nthreads = MAX_THREADPOOL_SIZE;
+
+  threads = default_threads;
+  if (nthreads > ARRAY_SIZE(default_threads)) {
+    threads = uv__malloc(nthreads * sizeof(threads[0]));
+    if (threads == NULL) {
+      nthreads = ARRAY_SIZE(default_threads);
+      threads = default_threads;
+    }
+  }
+
+  if (uv_cond_init(&cond))
+    abort();
+
+  if (uv_mutex_init(&mutex))
+    abort();
+
+  uv__queue_init(&wq);
+  uv__queue_init(&slow_io_pending_wq);
+  uv__queue_init(&run_slow_work_message);
+
+  if (uv_sem_init(&sem, 0))
+    abort();
+
+  config.flags = UV_THREAD_HAS_STACK_SIZE;
+  config.stack_size = 8u << 20;  /* 8 MB */
+
+  for (i = 0; i < nthreads; i++)
+    if (uv_thread_create_ex(threads + i, &config, worker, &sem))
+      abort();
+
+  for (i = 0; i < nthreads; i++)
+    uv_sem_wait(&sem);
+
+  uv_sem_destroy(&sem);
+}
+
+
+#ifndef _WIN32
+static void reset_once(void) {
+  uv_once_t child_once = UV_ONCE_INIT;
+  memcpy(&once, &child_once, sizeof(child_once));
+}
+#endif
+
+
+static void init_once(void) {
+#ifndef _WIN32
+  /* Re-initialize the threadpool after fork.
+   * Note that this discards the global mutex and condition as well
+   * as the work queue.
+   */
+  if (pthread_atfork(NULL, NULL, &reset_once))
+    abort();
+#endif
+  init_threads();
+}
+
+
+void uv__work_submit(uv_loop_t* loop,
+                     struct uv__work* w,
+                     enum uv__work_kind kind,
+                     void (*work)(struct uv__work* w),
+                     void (*done)(struct uv__work* w, int status)) {
+  uv_once(&once, init_once);
+  w->loop = loop;
+  w->work = work;
+  w->done = done;
+  post(&w->wq, kind);
+}
+
+
+/* TODO(bnoordhuis) teach libuv how to cancel file operations
+ * that go through io_uring instead of the thread pool.
+ */
+static int uv__work_cancel(uv_loop_t* loop, uv_req_t* req, struct uv__work* w) {
+  int cancelled;
+
+  uv_once(&once, init_once);  /* Ensure |mutex| is initialized. */
+  uv_mutex_lock(&mutex);
+  uv_mutex_lock(&w->loop->wq_mutex);
+
+  cancelled = !uv__queue_empty(&w->wq) && w->work != NULL;
+  if (cancelled)
+    uv__queue_remove(&w->wq);
+
+  uv_mutex_unlock(&w->loop->wq_mutex);
+  uv_mutex_unlock(&mutex);
+
+  if (!cancelled)
+    return UV_EBUSY;
+
+  w->work = uv__cancelled;
+  uv_mutex_lock(&loop->wq_mutex);
+  uv__queue_insert_tail(&loop->wq, &w->wq);
+  uv_async_send(&loop->wq_async);
+  uv_mutex_unlock(&loop->wq_mutex);
+
+  return 0;
+}
+
+
+void uv__work_done(uv_async_t* handle) {
+  struct uv__work* w;
+  uv_loop_t* loop;
+  struct uv__queue* q;
+  struct uv__queue wq;
+  int err;
+  int nevents;
+
+  loop = container_of(handle, uv_loop_t, wq_async);
+  uv_mutex_lock(&loop->wq_mutex);
+  uv__queue_move(&loop->wq, &wq);
+  uv_mutex_unlock(&loop->wq_mutex);
+
+  nevents = 0;
+
+  while (!uv__queue_empty(&wq)) {
+    q = uv__queue_head(&wq);
+    uv__queue_remove(q);
+
+    w = container_of(q, struct uv__work, wq);
+    err = (w->work == uv__cancelled) ? UV_ECANCELED : 0;
+    w->done(w, err);
+    nevents++;
+  }
+
+  /* This check accomplishes 2 things:
+   * 1. Even if the queue was empty, the call to uv__work_done() should count
+   *    as an event. Which will have been added by the event loop when
+   *    calling this callback.
+   * 2. Prevents accidental wrap around in case nevents == 0 events == 0.
+   */
+  if (nevents > 1) {
+    /* Subtract 1 to counter the call to uv__work_done(). */
+    uv__metrics_inc_events(loop, nevents - 1);
+    if (uv__get_internal_fields(loop)->current_timeout == 0)
+      uv__metrics_inc_events_waiting(loop, nevents - 1);
+  }
+}
+
+
+static void uv__queue_work(struct uv__work* w) {
+  uv_work_t* req = container_of(w, uv_work_t, work_req);
+
+  req->work_cb(req);
+}
+
+
+static void uv__queue_done(struct uv__work* w, int err) {
+  uv_work_t* req;
+
+  req = container_of(w, uv_work_t, work_req);
+  uv__req_unregister(req->loop);
+
+  if (req->after_work_cb == NULL)
+    return;
+
+  req->after_work_cb(req, err);
+}
+
+
+int uv_queue_work(uv_loop_t* loop,
+                  uv_work_t* req,
+                  uv_work_cb work_cb,
+                  uv_after_work_cb after_work_cb) {
+  if (work_cb == NULL)
+    return UV_EINVAL;
+
+  uv__req_init(loop, req, UV_WORK);
+  req->loop = loop;
+  req->work_cb = work_cb;
+  req->after_work_cb = after_work_cb;
+  uv__work_submit(loop,
+                  &req->work_req,
+                  UV__WORK_CPU,
+                  uv__queue_work,
+                  uv__queue_done);
+  return 0;
+}
+
+
+int uv_cancel(uv_req_t* req) {
+  struct uv__work* wreq;
+  uv_loop_t* loop;
+
+  switch (req->type) {
+  case UV_FS:
+    loop =  ((uv_fs_t*) req)->loop;
+    wreq = &((uv_fs_t*) req)->work_req;
+    break;
+  case UV_GETADDRINFO:
+    loop =  ((uv_getaddrinfo_t*) req)->loop;
+    wreq = &((uv_getaddrinfo_t*) req)->work_req;
+    break;
+  case UV_GETNAMEINFO:
+    loop = ((uv_getnameinfo_t*) req)->loop;
+    wreq = &((uv_getnameinfo_t*) req)->work_req;
+    break;
+  case UV_RANDOM:
+    loop = ((uv_random_t*) req)->loop;
+    wreq = &((uv_random_t*) req)->work_req;
+    break;
+  case UV_WORK:
+    loop =  ((uv_work_t*) req)->loop;
+    wreq = &((uv_work_t*) req)->work_req;
+    break;
+  default:
+    return UV_EINVAL;
+  }
+
+  return uv__work_cancel(loop, req, wreq);
+}