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Diffstat (limited to 'src/signal.c')
-rw-r--r-- | src/signal.c | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/src/signal.c b/src/signal.c new file mode 100644 index 0000000..3d7a9a8 --- /dev/null +++ b/src/signal.c @@ -0,0 +1,284 @@ +/* + * Asynchronous signal delivery functions. + * + * Copyright 2000-2010 Willy Tarreau <w@1wt.eu> + * + * 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. + * + */ + +#include <signal.h> +#include <string.h> + +#include <haproxy/errors.h> +#include <haproxy/signal.h> +#include <haproxy/task.h> + +/* Principle : we keep an in-order list of the first occurrence of all received + * signals. All occurrences of a same signal are grouped though. The signal + * queue does not need to be deeper than the number of signals we can handle. + * The handlers will be called asynchronously with the signal number. They can + * check themselves the number of calls by checking the descriptor this signal. + */ + +int signal_queue_len; /* length of signal queue, <= MAX_SIGNAL (1 entry per signal max) */ +int signal_queue[MAX_SIGNAL]; /* in-order queue of received signals */ +struct signal_descriptor signal_state[MAX_SIGNAL]; +sigset_t blocked_sig; +int signal_pending = 0; /* non-zero if t least one signal remains unprocessed */ + +DECLARE_STATIC_POOL(pool_head_sig_handlers, "sig_handlers", sizeof(struct sig_handler)); + +/* Common signal handler, used by all signals. Received signals are queued. + * Signal number zero has a specific status, as it cannot be delivered by the + * system, any function may call it to perform asynchronous signal delivery. + */ +void signal_handler(int sig) +{ + if (sig < 0 || sig >= MAX_SIGNAL) { + /* unhandled signal */ + signal(sig, SIG_IGN); + qfprintf(stderr, "Received unhandled signal %d. Signal has been disabled.\n", sig); + return; + } + + if (!signal_state[sig].count) { + /* signal was not queued yet */ + if (signal_queue_len < MAX_SIGNAL) + signal_queue[signal_queue_len++] = sig; + else + qfprintf(stderr, "Signal %d : signal queue is unexpectedly full.\n", sig); + } + + signal_state[sig].count++; + if (sig) + signal(sig, signal_handler); /* re-arm signal */ + + /* If the thread is TH_FL_SLEEPING we need to wake it */ + wake_thread(tid); +} + +/* Call handlers of all pending signals and clear counts and queue length. The + * handlers may unregister themselves by calling signal_register() while they + * are called, just like it is done with normal signal handlers. + * Note that it is more efficient to call the inline version which checks the + * queue length before getting here. + */ +void __signal_process_queue() +{ + int sig, cur_pos = 0; + struct signal_descriptor *desc; + sigset_t old_sig; + + /* block signal delivery during processing */ + ha_sigmask(SIG_SETMASK, &blocked_sig, &old_sig); + + /* It is important that we scan the queue forwards so that we can + * catch any signal that would have been queued by another signal + * handler. That allows real signal handlers to redistribute signals + * to tasks subscribed to signal zero. + */ + for (cur_pos = 0; cur_pos < signal_queue_len; cur_pos++) { + sig = signal_queue[cur_pos]; + desc = &signal_state[sig]; + if (desc->count) { + struct sig_handler *sh, *shb; + list_for_each_entry_safe(sh, shb, &desc->handlers, list) { + if ((sh->flags & SIG_F_TYPE_FCT) && sh->handler) + ((void (*)(struct sig_handler *))sh->handler)(sh); + else if ((sh->flags & SIG_F_TYPE_TASK) && sh->handler) + task_wakeup(sh->handler, TASK_WOKEN_SIGNAL); + } + desc->count = 0; + } + } + signal_queue_len = 0; + + /* restore signal delivery */ + ha_sigmask(SIG_SETMASK, &old_sig, NULL); +} + +/* perform minimal intializations */ +static void signal_init() +{ + int sig; + + signal_queue_len = 0; + memset(signal_queue, 0, sizeof(signal_queue)); + memset(signal_state, 0, sizeof(signal_state)); + + sigfillset(&blocked_sig); + sigdelset(&blocked_sig, SIGPROF); + /* man sigprocmask: If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are + generated while they are blocked, the result is undefined, unless + the signal was generated by kill(2), + sigqueue(3), or raise(3). + Do not ignore WDTSIG or DEBUGSIG either, or it may deadlock the + watchdog */ + sigdelset(&blocked_sig, SIGBUS); + sigdelset(&blocked_sig, SIGFPE); + sigdelset(&blocked_sig, SIGILL); + sigdelset(&blocked_sig, SIGSEGV); +#ifdef DEBUGSIG + sigdelset(&blocked_sig, DEBUGSIG); +#endif +#ifdef WDTSIG + sigdelset(&blocked_sig, WDTSIG); +#endif + for (sig = 0; sig < MAX_SIGNAL; sig++) + LIST_INIT(&signal_state[sig].handlers); +} + +/* + * This function should be called to unblock all signals + */ +void haproxy_unblock_signals() +{ + sigset_t set; + + /* Ensure signals are not blocked. Some shells or service managers may + * accidentally block all of our signals unfortunately, causing lots of + * zombie processes to remain in the background during reloads. + */ + sigemptyset(&set); + ha_sigmask(SIG_SETMASK, &set, NULL); +} + +/* releases all registered signal handlers */ +void deinit_signals() +{ + int sig; + struct sig_handler *sh, *shb; + + for (sig = 0; sig < MAX_SIGNAL; sig++) { + if (sig != SIGPROF) + signal(sig, SIG_DFL); + list_for_each_entry_safe(sh, shb, &signal_state[sig].handlers, list) { + LIST_DELETE(&sh->list); + pool_free(pool_head_sig_handlers, sh); + } + } +} + +/* Register a function and an integer argument on a signal. A pointer to the + * newly allocated sig_handler is returned, or NULL in case of any error. The + * caller is responsible for unregistering the function when not used anymore. + * Note that passing a NULL as the function pointer enables interception of the + * signal without processing, which is identical to SIG_IGN. If the signal is + * zero (which the system cannot deliver), only internal functions will be able + * to notify the registered functions. + */ +struct sig_handler *signal_register_fct(int sig, void (*fct)(struct sig_handler *), int arg) +{ + struct sig_handler *sh; + + if (sig < 0 || sig >= MAX_SIGNAL) + return NULL; + + if (sig) + signal(sig, fct ? signal_handler : SIG_IGN); + + if (!fct) + return NULL; + + sh = pool_alloc(pool_head_sig_handlers); + if (!sh) + return NULL; + + sh->handler = fct; + sh->arg = arg; + sh->flags = SIG_F_TYPE_FCT; + LIST_APPEND(&signal_state[sig].handlers, &sh->list); + return sh; +} + +/* Register a task and a wake-up reason on a signal. A pointer to the newly + * allocated sig_handler is returned, or NULL in case of any error. The caller + * is responsible for unregistering the task when not used anymore. Note that + * passing a NULL as the task pointer enables interception of the signal + * without processing, which is identical to SIG_IGN. If the signal is zero + * (which the system cannot deliver), only internal functions will be able to + * notify the registered functions. + */ +struct sig_handler *signal_register_task(int sig, struct task *task, int reason) +{ + struct sig_handler *sh; + + if (sig < 0 || sig >= MAX_SIGNAL) + return NULL; + + if (sig) + signal(sig, signal_handler); + + if (!task) + return NULL; + + sh = pool_alloc(pool_head_sig_handlers); + if (!sh) + return NULL; + + sh->handler = task; + sh->arg = reason & ~TASK_WOKEN_ANY; + sh->flags = SIG_F_TYPE_TASK; + LIST_APPEND(&signal_state[sig].handlers, &sh->list); + return sh; +} + +/* Immediately unregister a handler so that no further signals may be delivered + * to it. The struct is released so the caller may not reference it anymore. + */ +void signal_unregister_handler(struct sig_handler *handler) +{ + LIST_DELETE(&handler->list); + pool_free(pool_head_sig_handlers, handler); +} + +/* Immediately unregister a handler so that no further signals may be delivered + * to it. The handler struct does not need to be known, only the function or + * task pointer. This method is expensive because it scans all the list, so it + * should only be used for rare cases (eg: exit). The struct is released so the + * caller may not reference it anymore. + */ +void signal_unregister_target(int sig, void *target) +{ + struct sig_handler *sh, *shb; + + if (sig < 0 || sig >= MAX_SIGNAL) + return; + + if (!target) + return; + + list_for_each_entry_safe(sh, shb, &signal_state[sig].handlers, list) { + if (sh->handler == target) { + LIST_DELETE(&sh->list); + pool_free(pool_head_sig_handlers, sh); + break; + } + } +} + +/* + * Immedialtely unregister every handler assigned to a signal <sig>. + * Once the handler list is empty, the signal is ignored with SIG_IGN. + */ + +void signal_unregister(int sig) +{ + struct sig_handler *sh, *shb; + + if (sig < 0 || sig >= MAX_SIGNAL) + return; + + list_for_each_entry_safe(sh, shb, &signal_state[sig].handlers, list) { + LIST_DELETE(&sh->list); + pool_free(pool_head_sig_handlers, sh); + } + + signal(sig, SIG_IGN); +} + +INITCALL0(STG_PREPARE, signal_init); |