--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-ipc-heavy-traffic-deadlock-bug.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,159 @@
+/* Copyright libuv project 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 "task.h"
+#include "uv.h"
+
+#include <string.h>
+
+/* See test-ipc.c */
+void spawn_helper(uv_pipe_t* channel,
+                  uv_process_t* process,
+                  const char* helper);
+
+#define NUM_WRITES 256
+#define BUFFERS_PER_WRITE 3
+#define BUFFER_SIZE 0x2000 /* 8 kb. */
+#define BUFFER_CONTENT 42
+
+#define XFER_SIZE (NUM_WRITES * BUFFERS_PER_WRITE * BUFFER_SIZE)
+
+struct write_info {
+  uv_write_t write_req;
+  char buffers[BUFFER_SIZE][BUFFERS_PER_WRITE];
+};
+
+static uv_shutdown_t shutdown_req;
+
+static size_t bytes_written;
+static size_t bytes_read;
+
+static void write_cb(uv_write_t* req, int status) {
+  struct write_info* write_info =
+      container_of(req, struct write_info, write_req);
+  ASSERT_OK(status);
+  bytes_written += BUFFERS_PER_WRITE * BUFFER_SIZE;
+  free(write_info);
+}
+
+static void shutdown_cb(uv_shutdown_t* req, int status) {
+  ASSERT(status == 0 || status == UV_ENOTCONN);
+  uv_close((uv_handle_t*) req->handle, NULL);
+}
+
+static void do_write(uv_stream_t* handle) {
+  struct write_info* write_info;
+  uv_buf_t bufs[BUFFERS_PER_WRITE];
+  size_t i;
+  int r;
+
+  write_info = malloc(sizeof *write_info);
+  ASSERT_NOT_NULL(write_info);
+
+  for (i = 0; i < BUFFERS_PER_WRITE; i++) {
+    memset(&write_info->buffers[i], BUFFER_CONTENT, BUFFER_SIZE);
+    bufs[i] = uv_buf_init(write_info->buffers[i], BUFFER_SIZE);
+  }
+
+  r = uv_write(
+      &write_info->write_req, handle, bufs, BUFFERS_PER_WRITE, write_cb);
+  ASSERT_OK(r);
+}
+
+static void alloc_cb(uv_handle_t* handle,
+                     size_t suggested_size,
+                     uv_buf_t* buf) {
+  buf->base = malloc(suggested_size);
+  buf->len = (int) suggested_size;
+}
+
+#ifndef _WIN32
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
+static void read_cb(uv_stream_t* handle, ssize_t nread, const uv_buf_t* buf) {
+  ssize_t i;
+  int r;
+
+  ASSERT_GE(nread, 0);
+  bytes_read += nread;
+
+  for (i = 0; i < nread; i++)
+    ASSERT_EQ(buf->base[i], BUFFER_CONTENT);
+  free(buf->base);
+
+  if (bytes_read >= XFER_SIZE) {
+    r = uv_read_stop(handle);
+    ASSERT_OK(r);
+    r = uv_shutdown(&shutdown_req, handle, shutdown_cb);
+    ASSERT_OK(r);
+  }
+}
+
+static void do_writes_and_reads(uv_stream_t* handle) {
+  size_t i;
+  int r;
+
+  bytes_written = 0;
+  bytes_read = 0;
+
+  for (i = 0; i < NUM_WRITES; i++) {
+    do_write(handle);
+  }
+
+  r = uv_read_start(handle, alloc_cb, read_cb);
+  ASSERT_OK(r);
+
+  r = uv_run(handle->loop, UV_RUN_DEFAULT);
+  ASSERT_OK(r);
+
+  ASSERT_EQ(bytes_written, XFER_SIZE);
+  ASSERT_EQ(bytes_read, XFER_SIZE);
+}
+
+TEST_IMPL(ipc_heavy_traffic_deadlock_bug) {
+  uv_pipe_t pipe;
+  uv_process_t process;
+
+  spawn_helper(&pipe, &process, "ipc_helper_heavy_traffic_deadlock_bug");
+  do_writes_and_reads((uv_stream_t*) &pipe);
+
+  MAKE_VALGRIND_HAPPY(pipe.loop);
+  return 0;
+}
+
+int ipc_helper_heavy_traffic_deadlock_bug(void) {
+  uv_pipe_t pipe;
+  int r;
+
+  r = uv_pipe_init(uv_default_loop(), &pipe, 1);
+  ASSERT_OK(r);
+  r = uv_pipe_open(&pipe, 0);
+  ASSERT_OK(r);
+
+  notify_parent_process();
+  do_writes_and_reads((uv_stream_t*) &pipe);
+  uv_sleep(100);
+
+  MAKE_VALGRIND_HAPPY(uv_default_loop());
+  return 0;
+}