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-rw-r--r--tevent/tevent_signal.c291
1 files changed, 291 insertions, 0 deletions
diff --git a/tevent/tevent_signal.c b/tevent/tevent_signal.c
new file mode 100644
index 00000000..36907af6
--- /dev/null
+++ b/tevent/tevent_signal.c
@@ -0,0 +1,291 @@
+/*
+ Unix SMB/CIFS implementation.
+
+ common events code for signal events
+
+ Copyright (C) Andrew Tridgell 2007
+
+ 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 3 of the License, or
+ (at your option) any later version.
+
+ This program 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <signal.h>
+#include "replace.h"
+#include "system/filesys.h"
+#include "system/select.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 10
+
+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)
+
+
+/*
+ the poor design of signals means that this table must be static global
+*/
+static struct sig_state {
+ struct signal_event *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 signal_handler(int signum)
+{
+ char c = 0;
+ SIG_INCREMENT(sig_state->signal_count[signum]);
+ SIG_INCREMENT(sig_state->got_signal);
+ /* doesn't matter if this pipe overflows */
+ write(sig_state->pipe_hack[1], &c, 1);
+}
+
+#ifdef SA_SIGINFO
+/*
+ signal handler with SA_SIGINFO - redirects to registered signals
+*/
+static void 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;
+
+ 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
+
+/*
+ destroy a signal event
+*/
+static int signal_event_destructor(struct signal_event *se)
+{
+ se->event_ctx->num_signal_handlers--;
+ DLIST_REMOVE(sig_state->sig_handlers[se->signum], se);
+ 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 event_context *ev, struct fd_event *fde,
+ uint16_t flags, void *private)
+{
+ char c[16];
+ /* its non-blocking, doesn't matter if we read too much */
+ read(sig_state->pipe_hack[0], c, sizeof(c));
+}
+
+/*
+ add a signal event
+ return NULL on failure (memory allocation error)
+*/
+struct signal_event *common_event_add_signal(struct event_context *ev,
+ TALLOC_CTX *mem_ctx,
+ int signum,
+ int sa_flags,
+ event_signal_handler_t handler,
+ void *private_data)
+{
+ struct signal_event *se;
+
+ if (signum >= NUM_SIGNALS) {
+ 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 signal_event);
+ if (se == NULL) return NULL;
+
+ se->event_ctx = ev;
+ se->handler = handler;
+ se->private_data = private_data;
+ se->signum = signum;
+ se->sa_flags = sa_flags;
+
+ /* Ensure, no matter the destruction order, that we always have a handle on the global sig_state */
+ if (!talloc_reference(se, sig_state)) {
+ 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 = signal_handler;
+ act.sa_flags = sa_flags;
+#ifdef SA_SIGINFO
+ if (sa_flags & SA_SIGINFO) {
+ act.sa_handler = NULL;
+ act.sa_sigaction = 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(sig_state->sig_handlers[signum], se);
+
+ talloc_set_destructor(se, signal_event_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) {
+ pipe(sig_state->pipe_hack);
+ ev_set_blocking(sig_state->pipe_hack[0], false);
+ ev_set_blocking(sig_state->pipe_hack[1], false);
+ }
+ ev->pipe_fde = event_add_fd(ev, ev, sig_state->pipe_hack[0],
+ EVENT_FD_READ, signal_pipe_handler, NULL);
+ }
+ ev->num_signal_handlers++;
+
+ return se;
+}
+
+
+/*
+ check if a signal is pending
+ return != 0 if a signal was pending
+*/
+int common_event_check_signal(struct event_context *ev)
+{
+ int i;
+
+ if (!sig_state || !SIG_PENDING(sig_state->got_signal)) {
+ return 0;
+ }
+
+ for (i=0;i<NUM_SIGNALS+1;i++) {
+ struct signal_event *se, *next;
+ struct sigcounter counter = sig_state->signal_count[i];
+ uint32_t count = sig_count(counter);
+
+ if (count == 0) {
+ continue;
+ }
+ for (se=sig_state->sig_handlers[i];se;se=next) {
+ next = se->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;
+}
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