X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Ffatal-signal.c;h=66c04455ec98b91eeb4bbe07a211f71891b38d95;hb=780325b5b8d4c0552b4b7719e0a38200d99f6b08;hp=fc126caa95192a1c3577fbdb9dd38123c59558e9;hpb=34e63086edddcae06d7c1a4fa84fec0861e50758;p=sliver-openvswitch.git diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c index fc126caa9..66c04455e 100644 --- a/lib/fatal-signal.c +++ b/lib/fatal-signal.c @@ -1,5 +1,5 @@ /* - * Copyright (c) 2008, 2009 Nicira Networks. + * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -15,15 +15,29 @@ */ #include #include "fatal-signal.h" -#include #include #include #include #include +#include #include #include #include +#include "poll-loop.h" +#include "shash.h" +#include "sset.h" +#include "signals.h" +#include "socket-util.h" #include "util.h" +#include "vlog.h" + +#include "type-props.h" + +#ifndef SIG_ATOMIC_MAX +#define SIG_ATOMIC_MAX TYPE_MAXIMUM(sig_atomic_t) +#endif + +VLOG_DEFINE_THIS_MODULE(fatal_signal); /* Signals to catch. */ static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM }; @@ -33,7 +47,8 @@ static sigset_t fatal_signal_set; /* Hooks to call upon catching a signal */ struct hook { - void (*func)(void *aux); + void (*hook_cb)(void *aux); + void (*cancel_cb)(void *aux); void *aux; bool run_at_exit; }; @@ -41,82 +56,67 @@ struct hook { static struct hook hooks[MAX_HOOKS]; static size_t n_hooks; -/* Number of nesting signal blockers. */ -static int block_level = 0; - -/* Signal mask saved by outermost signal blocker. */ -static sigset_t saved_signal_mask; +static int signal_fds[2]; +static volatile sig_atomic_t stored_sig_nr = SIG_ATOMIC_MAX; -/* Disabled by fatal_signal_fork()? */ -static bool disabled; - -static void call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set); +static void fatal_signal_init(void); static void atexit_handler(void); static void call_hooks(int sig_nr); -/* Registers 'hook' to be called when a process termination signal is raised. - * If 'run_at_exit' is true, 'hook' is also called during normal process - * termination, e.g. when exit() is called or when main() returns. */ -void -fatal_signal_add_hook(void (*func)(void *aux), void *aux, bool run_at_exit) -{ - fatal_signal_block(); - assert(n_hooks < MAX_HOOKS); - hooks[n_hooks].func = func; - hooks[n_hooks].aux = aux; - hooks[n_hooks].run_at_exit = run_at_exit; - n_hooks++; - fatal_signal_unblock(); -} - -/* Blocks program termination signals until fatal_signal_unblock() is called. - * May be called multiple times with nesting; if so, fatal_signal_unblock() - * must be called the same number of times to unblock signals. - * - * This is needed while adjusting a data structure that will be accessed by a - * fatal signal hook, so that the hook is not invoked while the data structure - * is in an inconsistent state. */ -void -fatal_signal_block(void) +static void +fatal_signal_init(void) { static bool inited = false; + if (!inited) { size_t i; inited = true; + + xpipe_nonblocking(signal_fds); + sigemptyset(&fatal_signal_set); for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) { int sig_nr = fatal_signals[i]; struct sigaction old_sa; sigaddset(&fatal_signal_set, sig_nr); - if (sigaction(sig_nr, NULL, &old_sa)) { - ovs_fatal(errno, "sigaction"); - } + xsigaction(sig_nr, NULL, &old_sa); if (old_sa.sa_handler == SIG_DFL && signal(sig_nr, fatal_signal_handler) == SIG_ERR) { - ovs_fatal(errno, "signal"); + VLOG_FATAL("signal failed (%s)", strerror(errno)); } } atexit(atexit_handler); } - - if (++block_level == 1) { - call_sigprocmask(SIG_BLOCK, &fatal_signal_set, &saved_signal_mask); - } } -/* Unblocks program termination signals blocked by fatal_signal_block() is - * called. If multiple calls to fatal_signal_block() are nested, - * fatal_signal_unblock() must be called the same number of times to unblock - * signals. */ +/* Registers 'hook_cb' to be called when a process termination signal is + * raised. If 'run_at_exit' is true, 'hook_cb' is also called during normal + * process termination, e.g. when exit() is called or when main() returns. + * + * 'hook_cb' is not called immediately from the signal handler but rather the + * next time the poll loop iterates, so it is freed from the usual restrictions + * on signal handler functions. + * + * If the current process forks, fatal_signal_fork() may be called to clear the + * parent process's fatal signal hooks, so that 'hook_cb' is only called when + * the child terminates, not when the parent does. When fatal_signal_fork() is + * called, it calls the 'cancel_cb' function if it is nonnull, passing 'aux', + * to notify that the hook has been canceled. This allows the hook to free + * memory, etc. */ void -fatal_signal_unblock(void) +fatal_signal_add_hook(void (*hook_cb)(void *aux), void (*cancel_cb)(void *aux), + void *aux, bool run_at_exit) { - assert(block_level > 0); - if (--block_level == 0) { - call_sigprocmask(SIG_SETMASK, &saved_signal_mask, NULL); - } + fatal_signal_init(); + + ovs_assert(n_hooks < MAX_HOOKS); + hooks[n_hooks].hook_cb = hook_cb; + hooks[n_hooks].cancel_cb = cancel_cb; + hooks[n_hooks].aux = aux; + hooks[n_hooks].run_at_exit = run_at_exit; + n_hooks++; } /* Handles fatal signal number 'sig_nr'. @@ -131,20 +131,52 @@ fatal_signal_unblock(void) void fatal_signal_handler(int sig_nr) { - call_hooks(sig_nr); + ignore(write(signal_fds[1], "", 1)); + stored_sig_nr = sig_nr; +} + +/* Check whether a fatal signal has occurred and, if so, call the fatal signal + * hooks and exit. + * + * This function is called automatically by poll_block(), but specialized + * programs that may not always call poll_block() on a regular basis should + * also call it periodically. (Therefore, any function with "block" in its + * name should call fatal_signal_run() each time it is called, either directly + * or through poll_block(), because such functions can only used by specialized + * programs that can afford to block outside their main loop around + * poll_block().) + */ +void +fatal_signal_run(void) +{ + sig_atomic_t sig_nr; + + fatal_signal_init(); + + sig_nr = stored_sig_nr; + if (sig_nr != SIG_ATOMIC_MAX) { + VLOG_WARN("terminating with signal %d (%s)", + (int)sig_nr, signal_name(sig_nr)); + call_hooks(sig_nr); - /* Re-raise the signal with the default handling so that the program - * termination status reflects that we were killed by this signal */ - signal(sig_nr, SIG_DFL); - raise(sig_nr); + /* Re-raise the signal with the default handling so that the program + * termination status reflects that we were killed by this signal */ + signal(sig_nr, SIG_DFL); + raise(sig_nr); + } +} + +void +fatal_signal_wait(void) +{ + fatal_signal_init(); + poll_fd_wait(signal_fds[0], POLLIN); } static void atexit_handler(void) { - if (!disabled) { - call_hooks(0); - } + call_hooks(0); } static void @@ -159,16 +191,21 @@ call_hooks(int sig_nr) for (i = 0; i < n_hooks; i++) { struct hook *h = &hooks[i]; if (sig_nr || h->run_at_exit) { - h->func(h->aux); + h->hook_cb(h->aux); } } } } -static char **files; -static size_t n_files, max_files; +/* Files to delete on exit. */ +static struct sset files = SSET_INITIALIZER(&files); + +/* Has a hook function been registered with fatal_signal_add_hook() (and not + * cleared by fatal_signal_fork())? */ +static bool added_hook; static void unlink_files(void *aux); +static void cancel_files(void *aux); static void do_unlink_files(void); /* Registers 'file' to be unlinked when the program terminates via exit() or a @@ -176,18 +213,12 @@ static void do_unlink_files(void); void fatal_signal_add_file_to_unlink(const char *file) { - static bool added_hook = false; if (!added_hook) { added_hook = true; - fatal_signal_add_hook(unlink_files, NULL, true); + fatal_signal_add_hook(unlink_files, cancel_files, NULL, true); } - fatal_signal_block(); - if (n_files >= max_files) { - files = x2nrealloc(files, &max_files, sizeof *files); - } - files[n_files++] = xstrdup(file); - fatal_signal_unblock(); + sset_add(&files, file); } /* Unregisters 'file' from being unlinked when the program terminates via @@ -195,59 +226,71 @@ fatal_signal_add_file_to_unlink(const char *file) void fatal_signal_remove_file_to_unlink(const char *file) { - size_t i; + sset_find_and_delete(&files, file); +} - fatal_signal_block(); - for (i = 0; i < n_files; i++) { - if (!strcmp(files[i], file)) { - free(files[i]); - files[i] = files[--n_files]; - break; - } +/* Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'. + * Returns 0 if successful, otherwise a positive errno value. */ +int +fatal_signal_unlink_file_now(const char *file) +{ + int error = unlink(file) ? errno : 0; + if (error) { + VLOG_WARN("could not unlink \"%s\" (%s)", file, strerror(error)); } - fatal_signal_unblock(); + + fatal_signal_remove_file_to_unlink(file); + + return error; +} + +static void +unlink_files(void *aux OVS_UNUSED) +{ + do_unlink_files(); } static void -unlink_files(void *aux UNUSED) +cancel_files(void *aux OVS_UNUSED) { - do_unlink_files(); + sset_clear(&files); + added_hook = false; } static void do_unlink_files(void) { - size_t i; + const char *file; - for (i = 0; i < n_files; i++) { - unlink(files[i]); + SSET_FOR_EACH (file, &files) { + unlink(file); } } -/* Disables the fatal signal hook mechanism. Following a fork, one of the - * resulting processes can call this function to allow it to terminate without - * triggering fatal signal processing or removing files. Fatal signal - * processing is still enabled in the other process. */ +/* Clears all of the fatal signal hooks without executing them. If any of the + * hooks passed a 'cancel_cb' function to fatal_signal_add_hook(), then those + * functions will be called, allowing them to free resources, etc. + * + * Following a fork, one of the resulting processes can call this function to + * allow it to terminate without calling the hooks registered before calling + * this function. New hooks registered after calling this function will take + * effect normally. */ void fatal_signal_fork(void) { size_t i; - disabled = true; - - for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) { - int sig_nr = fatal_signals[i]; - if (signal(sig_nr, SIG_DFL) == SIG_IGN) { - signal(sig_nr, SIG_IGN); + for (i = 0; i < n_hooks; i++) { + struct hook *h = &hooks[i]; + if (h->cancel_cb) { + h->cancel_cb(h->aux); } } -} - -static void -call_sigprocmask(int how, sigset_t* new_set, sigset_t* old_set) -{ - int error = sigprocmask(how, new_set, old_set); - if (error) { - fprintf(stderr, "sigprocmask: %s\n", strerror(errno)); + n_hooks = 0; + + /* Raise any signals that we have already received with the default + * handler. */ + if (stored_sig_nr != SIG_ATOMIC_MAX) { + raise(stored_sig_nr); } }