opt: spawn use double fork

src/common/util.c

@@ -1,12 +1,14 @@
 /* See LICENSE.dwm file for copyright and license details. */
+#include "util.h"
 #include <fcntl.h>
+#include <signal.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <time.h>
-
-#include "util.h"
+#include <sys/resource.h>
+#include <wlr/util/log.h>
+#include <unistd.h>
 
 #define PCRE2_CODE_UNIT_WIDTH 8
 #include <pcre2.h>
@@ -205,4 +207,31 @@ void wl_list_swap(struct wl_list *l1, struct wl_list *l2) {
 		tmp2_prev->next = l1;
 		tmp2_next->prev = l1;
 	}
+}
+void restore_nofile_limit(void) {
+	struct rlimit rl;
+	if (getrlimit(RLIMIT_NOFILE, &rl) == 0) {
+		// Restore the soft limit to the hard limit
+		rl.rlim_cur = rl.rlim_max;
+		if (setrlimit(RLIMIT_NOFILE, &rl) != 0) {
+			wlr_log(WLR_DEBUG, "restore_nofile_limit: setrlimit failed");
+		}
+	} else {
+		wlr_log(WLR_DEBUG, "restore_nofile_limit: getrlimit failed");
+	}
+}
+
+void reset_child_environment(void) {
+	restore_nofile_limit();
+
+	setsid();
+
+	// Reset signal handlers
+	sigset_t set;
+	sigemptyset(&set);
+	sigprocmask(SIG_SETMASK, &set, NULL);
+
+	// Reset signal handlers to default
+	signal(SIGPIPE, SIG_DFL);
+	signal(SIGCHLD, SIG_DFL);
 }

src/common/util.h

@@ -1,5 +1,6 @@
 /* See LICENSE.dwm file for copyright and license details. */
 #include <wayland-util.h>
+#include <time.h>
 
 void die(const char *fmt, ...);
 void *ecalloc(size_t nmemb, size_t size);
@@ -12,4 +13,5 @@ char *join_strings(char *arr[], const char *sep);
 char *join_strings_with_suffix(char *arr[], const char *suffix,
 							   const char *sep);
 char *string_printf(const char *fmt, ...);
-void wl_list_swap(struct wl_list *l1, struct wl_list *l2);
+void wl_list_swap(struct wl_list *l1, struct wl_list *l2);
+void reset_child_environment(void);

src/dispatch/bind_define.h

@@ -907,22 +907,40 @@ int32_t spawn_shell(const Arg *arg) {
 	if (!arg->v)
 		return 0;
 
-	if (fork() == 0) {
-		signal(SIGSEGV, SIG_IGN);
-		signal(SIGABRT, SIG_IGN);
-		signal(SIGILL, SIG_IGN);
-
-		dup2(STDERR_FILENO, STDOUT_FILENO);
-		setsid();
-
-		execlp("sh", "sh", "-c", arg->v, (char *)NULL);
-		execlp("bash", "bash", "-c", arg->v, (char *)NULL);
-
-		wlr_log(WLR_DEBUG,
-				"mango: failed to execute command '%s' with shell: %s\n",
-				arg->v, strerror(errno));
-		_exit(EXIT_FAILURE);
+	pid_t child = fork();
+	if (child == -1) {
+		wlr_log_errno(WLR_ERROR, "spawn_shell: first fork failed");
+		return 0;
 	}
+
+	if (child == 0) {
+		// 重置子进程环境与信号
+		reset_child_environment();
+
+		pid_t grandchild = fork();
+		if (grandchild == -1) {
+			wlr_log_errno(WLR_ERROR, "spawn_shell: second fork failed");
+			_exit(EXIT_FAILURE);
+		}
+
+		if (grandchild == 0) {
+			// 孙进程负责实际执行
+			execlp("sh", "sh", "-c", arg->v, (char *)NULL);
+
+			// fallback to bash
+			execlp("bash", "bash", "-c", arg->v, (char *)NULL);
+
+			// 如果两个 shell 都启动失败
+			wlr_log_errno(WLR_ERROR, "spawn_shell: execlp failed for '%s'",
+						  (char *)arg->v);
+			_exit(EXIT_FAILURE);
+		}
+
+		// 子进程创建完孙进程后立即退出，主进程的 waitpid 瞬间返回
+		_exit(EXIT_SUCCESS);
+	}
+
+	waitpid(child, NULL, 0);
 	return 0;
 }
 
@@ -930,27 +948,49 @@ int32_t spawn(const Arg *arg) {
 	if (!arg->v)
 		return 0;
 
-	if (fork() == 0) {
-		signal(SIGSEGV, SIG_IGN);
-		signal(SIGABRT, SIG_IGN);
-		signal(SIGILL, SIG_IGN);
+	pid_t child = fork();
+	if (child == -1) {
+		wlr_log_errno(WLR_ERROR, "spawn: first fork failed");
+		return 0;
+	}
 
-		dup2(STDERR_FILENO, STDOUT_FILENO);
-		setsid();
+	if (child == 0) {
+		// 重置子进程环境与信号
+		reset_child_environment();
 
-		wordexp_t p;
-		if (wordexp(arg->v, &p, 0) != 0) {
-			wlr_log(WLR_DEBUG, "mango: wordexp failed for '%s'\n", arg->v);
+		// create second child
+		pid_t grandchild = fork();
+		if (grandchild == -1) {
+			wlr_log_errno(WLR_ERROR, "spawn: second fork failed");
 			_exit(EXIT_FAILURE);
 		}
 
-		execvp(p.we_wordv[0], p.we_wordv);
+		if (grandchild == 0) {
+			// execute actual command
+			wordexp_t p;
 
-		wlr_log(WLR_DEBUG, "mango: execvp '%s' failed: %s\n", p.we_wordv[0],
-				strerror(errno));
-		wordfree(&p);
-		_exit(EXIT_FAILURE);
+			if (wordexp(arg->v, &p, 0) != 0) {
+				wlr_log(WLR_ERROR, "mango: wordexp failed for '%s'",
+						(char *)arg->v);
+				_exit(EXIT_FAILURE);
+			}
+
+			// 执行成功的话，当前进程映像会被替换，自动释放堆内存
+			execvp(p.we_wordv[0], p.we_wordv);
+
+			// 只有 execvp 失败时才会走到这里
+			wlr_log_errno(WLR_ERROR, "spawn: execvp '%s' failed",
+						  p.we_wordv[0]);
+
+			wordfree(&p);
+			_exit(EXIT_FAILURE);
+		}
+
+		// 子进程退出，孙进程交由 init (systemd) 托管
+		_exit(EXIT_SUCCESS);
 	}
+
+	waitpid(child, NULL, 0);
 	return 0;
 }