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samba-mirror/lib/tevent/tevent_signal.c
Stefan Metzmacher 6211162d3e lib/tevent: change to LGPLv3+
metze
2009-02-16 08:53:25 +01:00

342 lines
8.8 KiB
C

/*
Unix SMB/CIFS implementation.
common events code for signal events
Copyright (C) Andrew Tridgell 2007
** NOTE! The following LGPL license applies to the tevent
** library. This does NOT imply that all of Samba is released
** under the LGPL
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "replace.h"
#include "system/filesys.h"
#include "system/wait.h"
#include "tevent.h"
#include "tevent_internal.h"
#include "tevent_util.h"
#define NUM_SIGNALS 64
/* maximum number of SA_SIGINFO signals to hold in the queue */
#define SA_INFO_QUEUE_COUNT 100
struct sigcounter {
uint32_t count;
uint32_t seen;
};
#define SIG_INCREMENT(s) (s).count++
#define SIG_SEEN(s, n) (s).seen += (n)
#define SIG_PENDING(s) ((s).seen != (s).count)
struct tevent_common_signal_list {
struct tevent_common_signal_list *prev, *next;
struct tevent_signal *se;
};
/*
the poor design of signals means that this table must be static global
*/
static struct sig_state {
struct tevent_common_signal_list *sig_handlers[NUM_SIGNALS+1];
struct sigaction *oldact[NUM_SIGNALS+1];
struct sigcounter signal_count[NUM_SIGNALS+1];
struct sigcounter got_signal;
int pipe_hack[2];
#ifdef SA_SIGINFO
/* with SA_SIGINFO we get quite a lot of info per signal */
siginfo_t *sig_info[NUM_SIGNALS+1];
struct sigcounter sig_blocked[NUM_SIGNALS+1];
#endif
} *sig_state;
/*
return number of sigcounter events not processed yet
*/
static uint32_t sig_count(struct sigcounter s)
{
if (s.count >= s.seen) {
return s.count - s.seen;
}
return 1 + (0xFFFFFFFF & ~(s.seen - s.count));
}
/*
signal handler - redirects to registered signals
*/
static void tevent_common_signal_handler(int signum)
{
char c = 0;
ssize_t res;
SIG_INCREMENT(sig_state->signal_count[signum]);
SIG_INCREMENT(sig_state->got_signal);
/* doesn't matter if this pipe overflows */
res = write(sig_state->pipe_hack[1], &c, 1);
}
#ifdef SA_SIGINFO
/*
signal handler with SA_SIGINFO - redirects to registered signals
*/
static void tevent_common_signal_handler_info(int signum, siginfo_t *info,
void *uctx)
{
uint32_t count = sig_count(sig_state->signal_count[signum]);
sig_state->sig_info[signum][count] = *info;
tevent_common_signal_handler(signum);
/* handle SA_SIGINFO */
if (count+1 == SA_INFO_QUEUE_COUNT) {
/* we've filled the info array - block this signal until
these ones are delivered */
sigset_t set;
sigemptyset(&set);
sigaddset(&set, signum);
sigprocmask(SIG_BLOCK, &set, NULL);
SIG_INCREMENT(sig_state->sig_blocked[signum]);
}
}
#endif
static int tevent_common_signal_list_destructor(struct tevent_common_signal_list *sl)
{
DLIST_REMOVE(sig_state->sig_handlers[sl->se->signum], sl);
return 0;
}
/*
destroy a signal event
*/
static int tevent_signal_destructor(struct tevent_signal *se)
{
struct tevent_common_signal_list *sl;
sl = talloc_get_type(se->additional_data,
struct tevent_common_signal_list);
if (se->event_ctx) {
DLIST_REMOVE(se->event_ctx->signal_events, se);
}
talloc_free(sl);
if (sig_state->sig_handlers[se->signum] == NULL) {
/* restore old handler, if any */
sigaction(se->signum, sig_state->oldact[se->signum], NULL);
sig_state->oldact[se->signum] = NULL;
#ifdef SA_SIGINFO
if (se->sa_flags & SA_SIGINFO) {
talloc_free(sig_state->sig_info[se->signum]);
sig_state->sig_info[se->signum] = NULL;
}
#endif
}
return 0;
}
/*
this is part of the pipe hack needed to avoid the signal race condition
*/
static void signal_pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
uint16_t flags, void *private)
{
char c[16];
ssize_t res;
/* its non-blocking, doesn't matter if we read too much */
res = read(sig_state->pipe_hack[0], c, sizeof(c));
}
/*
add a signal event
return NULL on failure (memory allocation error)
*/
struct tevent_signal *tevent_common_add_signal(struct tevent_context *ev,
TALLOC_CTX *mem_ctx,
int signum,
int sa_flags,
tevent_signal_handler_t handler,
void *private_data,
const char *handler_name,
const char *location)
{
struct tevent_signal *se;
struct tevent_common_signal_list *sl;
if (signum >= NUM_SIGNALS) {
errno = EINVAL;
return NULL;
}
/* the sig_state needs to be on a global context as it can last across
multiple event contexts */
if (sig_state == NULL) {
sig_state = talloc_zero(talloc_autofree_context(), struct sig_state);
if (sig_state == NULL) {
return NULL;
}
}
se = talloc(mem_ctx?mem_ctx:ev, struct tevent_signal);
if (se == NULL) return NULL;
se->event_ctx = ev;
se->signum = signum;
se->sa_flags = sa_flags;
se->handler = handler;
se->private_data = private_data;
se->handler_name = handler_name;
se->location = location;
se->additional_data = NULL;
sl = talloc(se, struct tevent_common_signal_list);
if (!sl) {
talloc_free(se);
return NULL;
}
sl->se = se;
se->additional_data = sl;
/* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
if (!talloc_reference(se, sig_state)) {
talloc_free(se);
return NULL;
}
/* only install a signal handler if not already installed */
if (sig_state->sig_handlers[signum] == NULL) {
struct sigaction act;
ZERO_STRUCT(act);
act.sa_handler = tevent_common_signal_handler;
act.sa_flags = sa_flags;
#ifdef SA_SIGINFO
if (sa_flags & SA_SIGINFO) {
act.sa_handler = NULL;
act.sa_sigaction = tevent_common_signal_handler_info;
if (sig_state->sig_info[signum] == NULL) {
sig_state->sig_info[signum] = talloc_array(sig_state, siginfo_t, SA_INFO_QUEUE_COUNT);
if (sig_state->sig_info[signum] == NULL) {
talloc_free(se);
return NULL;
}
}
}
#endif
sig_state->oldact[signum] = talloc(sig_state, struct sigaction);
if (sig_state->oldact[signum] == NULL) {
talloc_free(se);
return NULL;
}
if (sigaction(signum, &act, sig_state->oldact[signum]) == -1) {
talloc_free(se);
return NULL;
}
}
DLIST_ADD(se->event_ctx->signal_events, se);
DLIST_ADD(sig_state->sig_handlers[signum], sl);
talloc_set_destructor(se, tevent_signal_destructor);
talloc_set_destructor(sl, tevent_common_signal_list_destructor);
/* we need to setup the pipe hack handler if not already
setup */
if (ev->pipe_fde == NULL) {
if (sig_state->pipe_hack[0] == 0 &&
sig_state->pipe_hack[1] == 0) {
if (pipe(sig_state->pipe_hack) == -1) {
talloc_free(se);
return NULL;
}
ev_set_blocking(sig_state->pipe_hack[0], false);
ev_set_blocking(sig_state->pipe_hack[1], false);
}
ev->pipe_fde = tevent_add_fd(ev, ev, sig_state->pipe_hack[0],
TEVENT_FD_READ, signal_pipe_handler, NULL);
if (!ev->pipe_fde) {
talloc_free(se);
return NULL;
}
}
return se;
}
/*
check if a signal is pending
return != 0 if a signal was pending
*/
int tevent_common_check_signal(struct tevent_context *ev)
{
int i;
if (!sig_state || !SIG_PENDING(sig_state->got_signal)) {
return 0;
}
for (i=0;i<NUM_SIGNALS+1;i++) {
struct tevent_common_signal_list *sl, *next;
struct sigcounter counter = sig_state->signal_count[i];
uint32_t count = sig_count(counter);
if (count == 0) {
continue;
}
for (sl=sig_state->sig_handlers[i];sl;sl=next) {
struct tevent_signal *se = sl->se;
next = sl->next;
#ifdef SA_SIGINFO
if (se->sa_flags & SA_SIGINFO) {
int j;
for (j=0;j<count;j++) {
/* note the use of the sig_info array as a
ring buffer */
int ofs = ((count-1) + j) % SA_INFO_QUEUE_COUNT;
se->handler(ev, se, i, 1,
(void*)&sig_state->sig_info[i][ofs],
se->private_data);
}
if (SIG_PENDING(sig_state->sig_blocked[i])) {
/* we'd filled the queue, unblock the
signal now */
sigset_t set;
sigemptyset(&set);
sigaddset(&set, i);
SIG_SEEN(sig_state->sig_blocked[i],
sig_count(sig_state->sig_blocked[i]));
sigprocmask(SIG_UNBLOCK, &set, NULL);
}
if (se->sa_flags & SA_RESETHAND) {
talloc_free(se);
}
continue;
}
#endif
se->handler(ev, se, i, count, NULL, se->private_data);
if (se->sa_flags & SA_RESETHAND) {
talloc_free(se);
}
}
SIG_SEEN(sig_state->signal_count[i], count);
SIG_SEEN(sig_state->got_signal, count);
}
return 1;
}