--- /dev/null
+/*
+ * timout.c Advanced timeout handling for file system calls
+ * to avoid deadlocks on remote file shares.
+ *
+ * Version: 0.1 07-Sep-2011 Fink
+ *
+ * Copyright 2011 Werner Fink, 2011 SUSE LINUX Products GmbH, Germany.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * Author: Werner Fink <werner@suse.de>, 2011
+ */
+
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
+
+#ifndef USE_SOCKETPAIR
+# define USE_SOCKETPAIR 1
+#endif
+
+#ifdef _FEATURES_H
+# error Include local config.h before any system header file
+#endif
+#include "config.h" /* For _FILE_OFFSET_BITS */
+
+#include <errno.h>
+#include <pthread.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/select.h>
+#include <sys/stat.h>
+
+#include <unistd.h>
+#if USE_SOCKETPAIR
+# include <sys/socket.h>
+# include <netdb.h>
+# include <netinet/in.h>
+# ifndef SHUT_RD
+# define SHUT_RD 0
+# endif
+# ifndef SHUT_WR
+# define SHUT_WR 1
+# endif
+# undef pipe
+# define pipe(v) (((socketpair(AF_UNIX,SOCK_STREAM,0,v) < 0) || \
+ (shutdown((v)[1],SHUT_RD) < 0) || (shutdown((v)[0],SHUT_WR) < 0)) ? -1 : 0)
+#endif
+#include <wait.h>
+
+#include "timeout.h"
+
+#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L)
+# ifndef destructor
+# define destructor __destructor__
+# endif
+# ifndef constructor
+# define constructor __constructor__
+# endif
+# ifndef packed
+# define packed __packed__
+# endif
+# ifndef inline
+# define inline __inline__
+# endif
+# ifndef unused
+# define unused __unused__
+# endif
+# ifndef volatile
+# define volatile __volatile__
+# endif
+#endif
+#ifndef attribute
+# define attribute(attr) __attribute__(attr)
+#endif
+
+#if defined __GNUC__
+# undef strcpy
+# define strcpy(d,s) __builtin_strcpy((d),(s)) /* Without boundary check please */
+#endif
+
+/*
+ * The structure used for communication between the processes
+ */
+typedef struct _handle {
+ int errcode;
+ struct stat argument;
+ stat_t function;
+ size_t len;
+ char path[0];
+} attribute((packed)) handle_t;
+
+/*
+ * Using a forked process for doing e.g. stat(2) system call as this
+ * allows us to send e.g. SIGKILL to this process if it hangs in `D'
+ * state on a file share due a stalled NFS server. This does not work
+ * with (p)threads as SIGKILL would kill all threads including main.
+ */
+
+static volatile pid_t active;
+static int pipes[4] = {-1, -1, -1, -1};
+static char buf[PATH_MAX + sizeof(handle_t) + 1];
+
+static void sigchild(int sig attribute((unused)))
+{
+ pid_t pid = waitpid(active, NULL, WNOHANG|WUNTRACED);
+ if (pid <= 0)
+ return;
+ if (errno == ECHILD)
+ return;
+ active = 0;
+}
+
+static void attribute((constructor)) start(void)
+{
+ sigset_t sigset, oldset;
+ struct sigaction act;
+ ssize_t in;
+
+ if (pipes[1] >= 0) close(pipes[1]);
+ if (pipes[2] >= 0) close(pipes[2]);
+
+ if (pipe(&pipes[0]))
+ goto error;
+ if (pipe(&pipes[2]))
+ goto error;
+
+ memset(&act, 0, sizeof(act));
+ sigemptyset(&act.sa_mask);
+ act.sa_flags = SA_RESTART;
+ act.sa_handler = sigchild;
+ sigaction(SIGCHLD, &act, 0);
+
+ if ((active = fork()) < 0)
+ goto error;
+
+ if (active) {
+ close(pipes[0]);
+ close(pipes[3]);
+ pipes[0] = pipes[3] = -1;
+ return;
+ }
+
+ sigemptyset(&sigset);
+ sigaddset(&sigset, SIGALRM);
+ sigprocmask(SIG_BLOCK, &sigset, &oldset);
+
+ act.sa_handler = SIG_DFL;
+ sigaction(SIGCHLD, &act, 0);
+
+ close(pipes[1]);
+ close(pipes[2]);
+ dup2(pipes[0], STDIN_FILENO);
+ dup2(pipes[3], STDOUT_FILENO);
+ close(pipes[0]);
+ close(pipes[3]);
+ pipes[1] = pipes[2] = -1;
+ pipes[0] = pipes[3] = -1;
+
+ {
+ handle_t *restrict handle = (void*)&buf[0];
+
+ while ((in = read(STDIN_FILENO, handle, sizeof(buf))) > sizeof(handle_t)) {
+ if (handle->function(handle->path, &handle->argument) < 0)
+ handle->errcode = errno;
+ write(STDOUT_FILENO, &handle->errcode, sizeof(handle->errcode)+sizeof(handle->argument));
+ memset(handle, 0, sizeof(handle_t));
+ }
+ }
+ sigprocmask(SIG_SETMASK, &oldset, NULL);
+ exit(0);
+error:
+ if (pipes[0] >= 0) close(pipes[0]);
+ if (pipes[1] >= 0) close(pipes[1]);
+ if (pipes[2] >= 0) close(pipes[2]);
+ if (pipes[3] >= 0) close(pipes[3]);
+}
+
+static void /* attribute((destructor)) */ stop(void)
+{
+ if (active && waitpid(active, NULL, WNOHANG|WUNTRACED) == 0)
+ kill(active, SIGKILL);
+}
+
+static sigjmp_buf jenv;
+static void sigjump(int sig attribute((unused)))
+{
+ siglongjmp(jenv, 1);
+}
+
+/*
+ * External routine
+ */
+int timeout(stat_t function, const char *path, struct stat *restrict argument, time_t seconds)
+{
+ handle_t *restrict handle = (void*)&buf[0];
+ struct sigaction alrm_act, pipe_act, new_act;
+ sigset_t sigset, oldset;
+
+ if (active <= 0) /* Oops, last one failed therefore clear status and restart */
+ start();
+
+ memset(handle, 0, sizeof(handle_t));
+ handle->len = strlen(path) + 1;
+ if (handle->len >= PATH_MAX) {
+ errno = ENAMETOOLONG;
+ goto error;
+ }
+ handle->errcode = 0;
+ handle->argument = *argument;
+ handle->function = function;
+ strcpy(handle->path, path);
+
+ sigemptyset(&sigset);
+ sigaddset(&sigset, SIGALRM);
+ sigaddset(&sigset, SIGPIPE);
+ sigprocmask(SIG_UNBLOCK, &sigset, &oldset);
+
+ memset(&new_act, 0, sizeof(new_act));
+ sigemptyset(&new_act.sa_mask);
+ new_act.sa_flags = SA_RESETHAND;
+
+ if (sigsetjmp(jenv, 1))
+ goto timed;
+
+ new_act.sa_handler = sigjump;
+ sigaction(SIGALRM, &new_act, &alrm_act);
+ sigaction(SIGPIPE, &new_act, &pipe_act);
+ alarm(seconds);
+
+ write(pipes[1], handle, sizeof(handle_t)+handle->len);
+ read(pipes[2], &handle->errcode, sizeof(handle->errcode)+sizeof(handle->argument));
+
+ alarm(0);
+ sigaction(SIGPIPE, &pipe_act, NULL);
+ sigaction(SIGALRM, &alrm_act, NULL);
+
+ if (handle->errcode) {
+ errno = handle->errcode;
+ goto error;
+ }
+
+ *argument = handle->argument;
+ sigprocmask(SIG_SETMASK, &oldset, NULL);
+
+ return 0;
+timed:
+ (void) alarm(0);
+ sigaction(SIGPIPE, &pipe_act, NULL);
+ sigaction(SIGALRM, &alrm_act, NULL);
+ sigprocmask(SIG_SETMASK, &oldset, NULL);
+ stop();
+ errno = ETIMEDOUT;
+error:
+ return -1;
+}
+
+/*
+ * End of timeout.c
+ */
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