avoid leaving process zombies

while investigating JuliaLang#14434, I noticed that the test code there is creating zombies
to fix that, we need to avoid calling uv_close in the finalizer
until after the process has exited (or during atexit)

base/process.jl

@@ -289,7 +289,7 @@ type Process <: AbstractPipe
                    typemin(fieldtype(Process, :termsignal)),
                    false, Condition(), false, Condition())
         finalizer(this, uvfinalize)
-        this
+        return this
     end
 end
 pipe_reader(p::Process) = p.out
@@ -325,9 +325,12 @@ function _jl_spawn(cmd, argv, loop::Ptr{Void}, pp::Process,
 end
 
 function uvfinalize(proc::Process)
-    proc.handle != C_NULL && ccall(:jl_close_uv, Void, (Ptr{Void},), proc.handle)
-    disassociate_julia_struct(proc)
-    proc.handle = C_NULL
+    if proc.handle != C_NULL
+        disassociate_julia_struct(proc.handle)
+        ccall(:jl_close_uv, Void, (Ptr{Void},), proc.handle)
+        proc.handle = C_NULL
+    end
+    nothing
 end
 
 function uv_return_spawn(p::Ptr{Void}, exit_status::Int64, termsignal::Int32)

base/socket.jl

@@ -281,7 +281,7 @@ function TCPSocket()
         throw(UVError("failed to create tcp socket",err))
     end
     this.status = StatusInit
-    this
+    return this
 end
 
 type TCPServer <: LibuvServer
@@ -312,7 +312,7 @@ function TCPServer()
         throw(UVError("failed to create tcp server",err))
     end
     this.status = StatusInit
-    this
+    return this
 end
 
 isreadable(io::TCPSocket) = isopen(io) || nb_available(io) > 0

deps/checksums/libuv-cb6d0f875a5b8ca30cba45c0c1ef7442c87c1e68.tar.gz/md5

@@ -0,0 +1 @@
+c6a019d79d20eabc39619a04961c9a3b

deps/checksums/libuv-cb6d0f875a5b8ca30cba45c0c1ef7442c87c1e68.tar.gz/sha512

@@ -0,0 +1 @@
+478ab473244b01bef344892a75e09fef50da8fb1a7212e0257c53f3223de4fde5f6bd449eef34bc1f025481c7d9f854002acb6eb203b447a50a34bae4ad9dee4

deps/libuv.version

@@ -1,2 +1,2 @@
 LIBUV_BRANCH=julia-uv1.9.0
-LIBUV_SHA1=ecbd6eddfac4940ab8db57c73166a7378563ebd3
+LIBUV_SHA1=cb6d0f875a5b8ca30cba45c0c1ef7442c87c1e68

src/init.c

@@ -217,6 +217,7 @@ static struct uv_shutdown_queue_item *next_shutdown_queue_item(struct uv_shutdow
 
 void jl_init_timing(void);
 void jl_destroy_timing(void);
+void jl_uv_call_close_callback(jl_value_t *val);
 
 JL_DLLEXPORT void jl_atexit_hook(int exitcode)
 {
@@ -270,6 +271,13 @@ JL_DLLEXPORT void jl_atexit_hook(int exitcode)
                     continue;
                 }
                 switch(handle->type) {
+                case UV_PROCESS:
+                    // cause Julia to forget about the Process object
+                    if (handle->data)
+                        jl_uv_call_close_callback((jl_value_t*)handle->data);
+                    // and make libuv think it is already dead
+                    ((uv_process_t*)handle)->pid = 0;
+                    // fall-through
                 case UV_TTY:
                 case UV_UDP:
                 case UV_TCP:
@@ -283,7 +291,6 @@ JL_DLLEXPORT void jl_atexit_hook(int exitcode)
                 case UV_PREPARE:
                 case UV_CHECK:
                 case UV_SIGNAL:
-                case UV_PROCESS:
                 case UV_FILE:
                     // These will be shutdown as appropriate by jl_close_uv
                     jl_close_uv(handle);

src/jl_uv.c

@@ -78,17 +78,17 @@ void jl_init_signal_async(void)
 }
 #endif
 
-static void jl_uv_call_close_callback(jl_value_t *val)
+void jl_uv_call_close_callback(jl_value_t *val)
 {
     jl_value_t *args[2];
     args[0] = jl_get_global(jl_base_relative_to(((jl_datatype_t*)jl_typeof(val))->name->module),
             jl_symbol("_uv_hook_close")); // topmod(typeof(val))._uv_hook_close
     args[1] = val;
     assert(args[0]);
-    jl_apply(args, 2);
+    jl_apply(args, 2); // TODO: wrap in try-catch?
 }
 
-JL_DLLEXPORT void jl_uv_closeHandle(uv_handle_t *handle)
+static void jl_uv_closeHandle(uv_handle_t *handle)
 {
     // if the user killed a stdio handle,
     // revert back to direct stdio FILE* writes
@@ -107,7 +107,7 @@ JL_DLLEXPORT void jl_uv_closeHandle(uv_handle_t *handle)
     free(handle);
 }
 
-JL_DLLEXPORT void jl_uv_shutdownCallback(uv_shutdown_t *req, int status)
+static void jl_uv_shutdownCallback(uv_shutdown_t *req, int status)
 {
     /*
      * This happens if the remote machine closes the connecition while we're
@@ -180,8 +180,21 @@ JL_DLLEXPORT int jl_init_pipe(uv_pipe_t *pipe, int writable, int readable,
      return err;
 }
 
+static void jl_proc_exit_cleanup(uv_process_t *process, int64_t exit_status, int term_signal)
+{
+    uv_close((uv_handle_t*)process, (uv_close_cb)&free);
+}
+
 JL_DLLEXPORT void jl_close_uv(uv_handle_t *handle)
 {
+    if (handle->type == UV_PROCESS && ((uv_process_t*)handle)->pid != 0) {
+        // take ownership of this handle,
+        // so we can waitpid for the resource to exit and avoid leaving zombies
+        assert(handle->data == NULL); // make sure Julia has forgotten about it already
+        ((uv_process_t*)handle)->exit_cb = jl_proc_exit_cleanup;
+        return;
+    }
+
     if (handle->type == UV_FILE) {
         uv_fs_t req;
         jl_uv_file_t *fd = (jl_uv_file_t*)handle;