Add timeout.c/timeout.h for static background process for doing the stat system calls

Signed-off-by: Werner Fink <werner@suse.de>

3 files changed, 306 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index b42a4d7..bde0f6f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,6 @@
+	* Add timeout.c/timeout.h for static background process which is able
+	  to read the file name from pipe, does the stat(2) system call, and
+	  writes the result back to a pipe.
 	* Really add ASCII null at command string in add_proc() of pstree.c
 
 Changes in 22.16
diff --git a/src/timeout.c b/src/timeout.c
new file mode 100644
index 0000000..1fe0354
--- /dev/null
+++ b/src/timeout.c
@@ -0,0 +1,267 @@
+/*
+ * 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
+ */
diff --git a/src/timeout.h b/src/timeout.h
new file mode 100644
index 0000000..546c13b
--- /dev/null
+++ b/src/timeout.h
@@ -0,0 +1,36 @@
+/*
+ * timout.h	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 _TIMEOUT_H
+#define _TIMEOUT_H
+
+#include "config.h"		/* For _FILE_OFFSET_BITS */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <limits.h>
+
+#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L)
+# ifndef  restrict
+#  define restrict		__restrict__
+# endif
+#endif
+
+typedef int (*stat_t)(const char *, struct stat *restrict);
+extern int timeout(stat_t, const char *, struct stat *restrict, time_t);
+
+#endif