Processing (Linux): use posix_spawnp for better performance

Author: CarterLi

src/common/processing_linux.c

@@ -11,6 +11,7 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <sys/wait.h>
+#include <spawn.h>
 
 #if defined(__FreeBSD__) || defined(__APPLE__)
     #include <sys/types.h>
@@ -33,6 +34,10 @@
     #include <image.h>
 #endif
 
+#ifndef environ
+extern char** environ;
+#endif
+
 enum { FF_PIPE_BUFSIZ = 8192 };
 
 static inline int ffPipe2(int* fds, int flags)
@@ -56,27 +61,38 @@ const char* ffProcessAppendOutput(FFstrbuf* buffer, char* const argv[], bool use
     if(ffPipe2(pipes, O_CLOEXEC) == -1)
         return "pipe() failed";
 
-    pid_t childPid = fork();
-    if(childPid == -1)
-    {
-        close(pipes[0]);
-        close(pipes[1]);
-        return "fork() failed";
-    }
+    posix_spawn_file_actions_t file_actions;
+    posix_spawn_file_actions_init(&file_actions);
+    posix_spawn_file_actions_adddup2(&file_actions, pipes[1], useStdErr ? STDERR_FILENO : STDOUT_FILENO);
+    posix_spawn_file_actions_addopen(&file_actions, useStdErr ? STDOUT_FILENO : STDERR_FILENO, "/dev/null", O_WRONLY, 0);
+    pid_t childPid = -1;
 
-    //Child
-    if(childPid == 0)
+    char* oldLang = NULL;
+    int langIndex = -1;
+    for (int i = 0; environ[i] != NULL; i++)
     {
-        int nullFile = open("/dev/null", O_WRONLY | O_CLOEXEC);
-        dup2(pipes[1], useStdErr ? STDERR_FILENO : STDOUT_FILENO);
-        dup2(nullFile, useStdErr ? STDOUT_FILENO : STDERR_FILENO);
-        setenv("LANG", "C", 1);
-        execvp(argv[0], argv);
-        _exit(127);
+        if (ffStrStartsWith(environ[i], "LANG="))
+        {
+            oldLang = environ[i];
+            environ[i] = (char*) "LANG=C";
+            langIndex = i;
+            break;
+        }
     }
 
-    //Parent
+    int ret = posix_spawnp(&childPid, argv[0], &file_actions, NULL, argv, environ);
+
+    if (oldLang)
+        environ[langIndex] = oldLang;
+
+    posix_spawn_file_actions_destroy(&file_actions);
+
     close(pipes[1]);
+    if (ret != 0)
+    {
+        close(pipes[0]);
+        return "posix_spawnp() failed";
+    }
 
     int FF_AUTO_CLOSE_FD childPipeFd = pipes[0];
     char str[FF_PIPE_BUFSIZ];
@@ -86,20 +102,30 @@ const char* ffProcessAppendOutput(FFstrbuf* buffer, char* const argv[], bool use
         if (timeout >= 0)
         {
             struct pollfd pollfd = { childPipeFd, POLLIN, 0 };
-            if (poll(&pollfd, 1, timeout) == 0)
+            int pollret = poll(&pollfd, 1, timeout);
+            if (pollret == 0)
             {
                 kill(childPid, SIGTERM);
                 waitpid(childPid, NULL, 0);
                 return "poll(&pollfd, 1, timeout) timeout (try increasing --processing-timeout)";
             }
-            else if (errno == EINTR)
+            else if (pollret < 0)
             {
-                // The child process has been terminated. See `chldSignalHandler` in `common/init.c`
-                if (waitpid(childPid, NULL, WNOHANG) == childPid)
+                if (errno == EINTR)
+                {
+                    // The child process has been terminated. See `chldSignalHandler` in `common/init.c`
+                    if (waitpid(childPid, NULL, WNOHANG) == childPid)
+                    {
+                        // Read remaining data from the pipe
+                        fcntl(childPipeFd, F_SETFL, O_CLOEXEC | O_NONBLOCK);
+                        childPid = -1;
+                    }
+                }
+                else
                 {
-                    // Read remaining data from the pipe
-                    fcntl(childPipeFd, F_SETFL, O_CLOEXEC | O_NONBLOCK);
-                    childPid = -1;
+                    kill(childPid, SIGTERM);
+                    waitpid(childPid, NULL, 0);
+                    return "poll(&pollfd, 1, timeout) error";
                 }
             }
             else if (pollfd.revents & POLLERR)