blob: e996c46d6d03566e4e3a32feea03faa7789bd6de [file] [log] [blame]
/*
* 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 <proto/signal.h>
#include <proto/log.h>
#include <proto/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];
struct pool_head *pool2_sig_handlers = NULL;
sigset_t blocked_sig;
int signal_pending = 0; /* non-zero if t least one signal remains unprocessed */
__decl_hathreads(HA_SPINLOCK_T signals_lock);
/* 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 */
}
/* 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;
if (HA_SPIN_TRYLOCK(SIGNALS_LOCK, &signals_lock))
return;
/* block signal delivery during processing */
sigprocmask(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, sh->arg | TASK_WOKEN_SIGNAL);
}
desc->count = 0;
}
}
signal_queue_len = 0;
/* restore signal delivery */
sigprocmask(SIG_SETMASK, &old_sig, NULL);
HA_SPIN_UNLOCK(SIGNALS_LOCK, &signals_lock);
}
/* perform minimal intializations, report 0 in case of error, 1 if OK. */
int signal_init()
{
int sig;
signal_queue_len = 0;
memset(signal_queue, 0, sizeof(signal_queue));
memset(signal_state, 0, sizeof(signal_state));
HA_SPIN_INIT(&signals_lock);
/* Ensure signals are not blocked. Some shells or service managers may
* accidently block all of our signals unfortunately, causing lots of
* zombie processes to remain in the background during reloads.
*/
sigemptyset(&blocked_sig);
/* Ensure that SIGUSR2 is blocked until the end of configuration
* parsing We don't want the process to be killed by an unregistered
* USR2 signal when the master-worker is reloading */
sigaddset(&blocked_sig, SIGUSR2);
sigprocmask(SIG_SETMASK, &blocked_sig, NULL);
sigfillset(&blocked_sig);
sigdelset(&blocked_sig, SIGPROF);
for (sig = 0; sig < MAX_SIGNAL; sig++)
LIST_INIT(&signal_state[sig].handlers);
pool2_sig_handlers = create_pool("sig_handlers", sizeof(struct sig_handler), MEM_F_SHARED);
return pool2_sig_handlers != 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_DEL(&sh->list);
pool_free2(pool2_sig_handlers, sh);
}
}
HA_SPIN_DESTROY(&signals_lock);
}
/* 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_alloc2(pool2_sig_handlers);
if (!sh)
return NULL;
sh->handler = fct;
sh->arg = arg;
sh->flags = SIG_F_TYPE_FCT;
LIST_ADDQ(&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_alloc2(pool2_sig_handlers);
if (!sh)
return NULL;
sh->handler = task;
sh->arg = reason & ~TASK_WOKEN_ANY;
sh->flags = SIG_F_TYPE_TASK;
LIST_ADDQ(&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_DEL(&handler->list);
pool_free2(pool2_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_DEL(&sh->list);
pool_free2(pool2_sig_handlers, sh);
break;
}
}
}