X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=lib%2Ffatal-signal.c;h=64b045d37d992ac7657193819161b77a023b9f58;hb=fe55ad159d8fd396a9e4914a03eea93d096d03b1;hp=ff011363e307b8dce9b1e1a70a6a1b3cef6da975;hpb=411baaacb8672cd9b231328b77a5f1c8a11aad9c;p=openvswitch diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c index ff011363..64b045d3 100644 --- a/lib/fatal-signal.c +++ b/lib/fatal-signal.c @@ -20,12 +20,18 @@ #include #include #include +#include #include #include #include +#include "poll-loop.h" #include "shash.h" +#include "socket-util.h" #include "util.h" +#define THIS_MODULE VLM_fatal_signal +#include "vlog.h" + /* Signals to catch. */ static const int fatal_signals[] = { SIGTERM, SIGINT, SIGHUP, SIGALRM }; @@ -42,49 +48,32 @@ 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; + + if (pipe(signal_fds)) { + ovs_fatal(errno, "could not create pipe"); + } + set_nonblocking(signal_fds[0]); + set_nonblocking(signal_fds[1]); + sigemptyset(&fatal_signal_set); for (i = 0; i < ARRAY_SIZE(fatal_signals); i++) { int sig_nr = fatal_signals[i]; @@ -101,23 +90,24 @@ fatal_signal_block(void) } 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' 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. + * + * The hook 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. */ void -fatal_signal_unblock(void) +fatal_signal_add_hook(void (*func)(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(); + 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++; } /* Handles fatal signal number 'sig_nr'. @@ -132,12 +122,29 @@ 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; +} + +void +fatal_signal_run(void) +{ + int sig_nr = stored_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); + if (sig_nr != SIG_ATOMIC_MAX) { + 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); + } +} + +void +fatal_signal_wait(void) +{ + poll_fd_wait(signal_fds[0], POLLIN); } static void @@ -182,11 +189,9 @@ fatal_signal_add_file_to_unlink(const char *file) fatal_signal_add_hook(unlink_files, NULL, true); } - fatal_signal_block(); if (!shash_find(&files, file)) { shash_add(&files, file, NULL); } - fatal_signal_unblock(); } /* Unregisters 'file' from being unlinked when the program terminates via @@ -196,12 +201,25 @@ fatal_signal_remove_file_to_unlink(const char *file) { struct shash_node *node; - fatal_signal_block(); node = shash_find(&files, file); if (node) { shash_delete(&files, node); } - fatal_signal_unblock(); +} + +/* 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_remove_file_to_unlink(file); + + return error; } static void @@ -237,13 +255,10 @@ fatal_signal_fork(void) signal(sig_nr, SIG_IGN); } } -} - -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)); + + /* Raise any signals that we have already received with the default + * handler. */ + if (stored_sig_nr != SIG_ATOMIC_MAX) { + raise(stored_sig_nr); } }