1 files changed, 484 insertions, 0 deletions

diff --git a/ctdb/lib/tevent/tevent_signal.c b/ctdb/lib/tevent/tevent_signal.c
new file mode 100644
index 0000000000..b5a56ef03a
--- /dev/null
+++ b/ctdb/lib/tevent/tevent_signal.c
@@ -0,0 +1,484 @@
+/* 
+   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"
+
+/* maximum number of SA_SIGINFO signals to hold in the queue.
+  NB. This *MUST* be a power of 2, in order for the ring buffer
+  wrap to work correctly. Thanks to Petr Vandrovec <petr@vandrovec.name>
+  for this. */
+
+#define TEVENT_SA_INFO_QUEUE_COUNT 64
+
+struct tevent_sigcounter {
+	uint32_t count;
+	uint32_t seen;
+};
+
+#define TEVENT_SIG_INCREMENT(s) (s).count++
+#define TEVENT_SIG_SEEN(s, n) (s).seen += (n)
+#define TEVENT_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 tevent_sig_state {
+	struct tevent_common_signal_list *sig_handlers[TEVENT_NUM_SIGNALS+1];
+	struct sigaction *oldact[TEVENT_NUM_SIGNALS+1];
+	struct tevent_sigcounter signal_count[TEVENT_NUM_SIGNALS+1];
+	struct tevent_sigcounter got_signal;
+#ifdef SA_SIGINFO
+	/* with SA_SIGINFO we get quite a lot of info per signal */
+	siginfo_t *sig_info[TEVENT_NUM_SIGNALS+1];
+	struct tevent_sigcounter sig_blocked[TEVENT_NUM_SIGNALS+1];
+#endif
+} *sig_state;
+
+/*
+  return number of sigcounter events not processed yet
+*/
+static uint32_t tevent_sig_count(struct tevent_sigcounter s)
+{
+	return s.count - s.seen;
+}
+
+/*
+  signal handler - redirects to registered signals
+*/
+static void tevent_common_signal_handler(int signum)
+{
+	char c = 0;
+	struct tevent_common_signal_list *sl;
+	struct tevent_context *ev = NULL;
+	int saved_errno = errno;
+
+	TEVENT_SIG_INCREMENT(sig_state->signal_count[signum]);
+	TEVENT_SIG_INCREMENT(sig_state->got_signal);
+
+	/* Write to each unique event context. */
+	for (sl = sig_state->sig_handlers[signum]; sl; sl = sl->next) {
+		if (sl->se->event_ctx && sl->se->event_ctx != ev) {
+			ev = sl->se->event_ctx;
+			/* doesn't matter if this pipe overflows */
+			(void) write(ev->pipe_fds[1], &c, 1);
+		}
+	}
+
+	errno = saved_errno;
+}
+
+#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 = tevent_sig_count(sig_state->signal_count[signum]);
+	/* sig_state->signal_count[signum].seen % TEVENT_SA_INFO_QUEUE_COUNT
+	 * is the base of the unprocessed signals in the ringbuffer. */
+	uint32_t ofs = (sig_state->signal_count[signum].seen + count) %
+				TEVENT_SA_INFO_QUEUE_COUNT;
+	sig_state->sig_info[signum][ofs] = *info;
+
+	tevent_common_signal_handler(signum);
+
+	/* handle SA_SIGINFO */
+	if (count+1 == TEVENT_SA_INFO_QUEUE_COUNT) {
+		/* we've filled the info array - block this signal until
+		   these ones are delivered */
+#ifdef HAVE_UCONTEXT_T
+		/*
+		 * This is the only way for this to work.
+		 * By default signum is blocked inside this
+		 * signal handler using a temporary mask,
+		 * but what we really need to do now is
+		 * block it in the callers mask, so it
+		 * stays blocked when the temporary signal
+		 * handler mask is replaced when we return
+		 * from here. The callers mask can be found
+		 * in the ucontext_t passed in as the
+		 * void *uctx argument.
+		 */
+		ucontext_t *ucp = (ucontext_t *)uctx;
+		sigaddset(&ucp->uc_sigmask, signum);
+#else
+		/*
+		 * WARNING !!! WARNING !!!!
+		 *
+		 * This code doesn't work.
+		 * By default signum is blocked inside this
+		 * signal handler, but calling sigprocmask
+		 * modifies the temporary signal mask being
+		 * used *inside* this handler, which will be
+		 * replaced by the callers signal mask once
+		 * we return from here. See Samba
+		 * bug #9550 for details.
+		 */
+		sigset_t set;
+		sigemptyset(&set);
+		sigaddset(&set, signum);
+		sigprocmask(SIG_BLOCK, &set, NULL);
+#endif
+		TEVENT_SIG_INCREMENT(sig_state->sig_blocked[signum]);
+	}
+}
+#endif
+
+static int tevent_common_signal_list_destructor(struct tevent_common_signal_list *sl)
+{
+	if (sig_state->sig_handlers[sl->se->signum]) {
+		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 */
+		if (sig_state->oldact[se->signum]) {
+			sigaction(se->signum, sig_state->oldact[se->signum], NULL);
+			sig_state->oldact[se->signum] = NULL;
+		}
+#ifdef SA_SIGINFO
+		if (se->sa_flags & SA_SIGINFO) {
+			if (sig_state->sig_info[se->signum]) {
+				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];
+	/* its non-blocking, doesn't matter if we read too much */
+	(void) read(fde->fd, 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;
+	sigset_t set, oldset;
+
+	if (signum >= TEVENT_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(NULL, struct tevent_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;
+	}
+
+	/* we need to setup the pipe hack handler if not already
+	   setup */
+	if (ev->pipe_fde == NULL) {
+		if (pipe(ev->pipe_fds) == -1) {
+			talloc_free(se);
+			return NULL;
+		}
+		ev_set_blocking(ev->pipe_fds[0], false);
+		ev_set_blocking(ev->pipe_fds[1], false);
+		ev->pipe_fde = tevent_add_fd(ev, ev, ev->pipe_fds[0],
+					     TEVENT_FD_READ,
+					     signal_pipe_handler, NULL);
+		if (!ev->pipe_fde) {
+			close(ev->pipe_fds[0]);
+			close(ev->pipe_fds[1]);
+			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_zero_array(sig_state, siginfo_t,
+							  TEVENT_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);
+
+	/* Make sure the signal doesn't come in while we're mangling list. */
+	sigemptyset(&set);
+	sigaddset(&set, signum);
+	sigprocmask(SIG_BLOCK, &set, &oldset);
+	DLIST_ADD(sig_state->sig_handlers[signum], sl);
+	sigprocmask(SIG_SETMASK, &oldset, NULL);
+
+	talloc_set_destructor(se, tevent_signal_destructor);
+	talloc_set_destructor(sl, tevent_common_signal_list_destructor);
+
+	return se;
+}
+
+struct tevent_se_exists {
+	struct tevent_se_exists **myself;
+};
+
+static int tevent_se_exists_destructor(struct tevent_se_exists *s)
+{
+	*s->myself = NULL;
+	return 0;
+}
+
+/*
+  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 || !TEVENT_SIG_PENDING(sig_state->got_signal)) {
+		return 0;
+	}
+	
+	for (i=0;i<TEVENT_NUM_SIGNALS+1;i++) {
+		struct tevent_common_signal_list *sl, *next;
+		struct tevent_sigcounter counter = sig_state->signal_count[i];
+		uint32_t count = tevent_sig_count(counter);
+#ifdef SA_SIGINFO
+		/* Ensure we null out any stored siginfo_t entries
+		 * after processing for debugging purposes. */
+		bool clear_processed_siginfo = false;
+#endif
+
+		if (count == 0) {
+			continue;
+		}
+		for (sl=sig_state->sig_handlers[i];sl;sl=next) {
+			struct tevent_signal *se = sl->se;
+			struct tevent_se_exists *exists;
+
+			next = sl->next;
+
+			/*
+			 * We have to be careful to not touch "se"
+			 * after it was deleted in its handler. Thus
+			 * we allocate a child whose destructor will
+			 * tell by nulling out itself that its parent
+			 * is gone.
+			 */
+			exists = talloc(se, struct tevent_se_exists);
+			if (exists == NULL) {
+				continue;
+			}
+			exists->myself = &exists;
+			talloc_set_destructor(
+				exists, tevent_se_exists_destructor);
+
+#ifdef SA_SIGINFO
+			if (se->sa_flags & SA_SIGINFO) {
+				uint32_t j;
+
+				clear_processed_siginfo = true;
+
+				for (j=0;j<count;j++) {
+					/* sig_state->signal_count[i].seen
+					 * % TEVENT_SA_INFO_QUEUE_COUNT is
+					 * the base position of the unprocessed
+					 * signals in the ringbuffer. */
+					uint32_t ofs = (counter.seen + j)
+						% TEVENT_SA_INFO_QUEUE_COUNT;
+					se->handler(ev, se, i, 1,
+						    (void*)&sig_state->sig_info[i][ofs], 
+						    se->private_data);
+					if (!exists) {
+						break;
+					}
+				}
+#ifdef SA_RESETHAND
+				if (exists && (se->sa_flags & SA_RESETHAND)) {
+					talloc_free(se);
+				}
+#endif
+				talloc_free(exists);
+				continue;
+			}
+#endif
+			se->handler(ev, se, i, count, NULL, se->private_data);
+#ifdef SA_RESETHAND
+			if (exists && (se->sa_flags & SA_RESETHAND)) {
+				talloc_free(se);
+			}
+#endif
+			talloc_free(exists);
+		}
+
+#ifdef SA_SIGINFO
+		if (clear_processed_siginfo) {
+			uint32_t j;
+			for (j=0;j<count;j++) {
+				uint32_t ofs = (counter.seen + j)
+					% TEVENT_SA_INFO_QUEUE_COUNT;
+				memset((void*)&sig_state->sig_info[i][ofs],
+					'\0',
+					sizeof(siginfo_t));
+			}
+		}
+#endif
+
+		TEVENT_SIG_SEEN(sig_state->signal_count[i], count);
+		TEVENT_SIG_SEEN(sig_state->got_signal, count);
+
+#ifdef SA_SIGINFO
+		if (TEVENT_SIG_PENDING(sig_state->sig_blocked[i])) {
+			/* We'd filled the queue, unblock the
+			   signal now the queue is empty again.
+			   Note we MUST do this after the
+			   TEVENT_SIG_SEEN(sig_state->signal_count[i], count)
+			   call to prevent a new signal running
+			   out of room in the sig_state->sig_info[i][]
+			   ring buffer. */
+			sigset_t set;
+			sigemptyset(&set);
+			sigaddset(&set, i);
+			TEVENT_SIG_SEEN(sig_state->sig_blocked[i],
+				 tevent_sig_count(sig_state->sig_blocked[i]));
+			sigprocmask(SIG_UNBLOCK, &set, NULL);
+		}
+#endif
+	}
+
+	return 1;
+}
+
+void tevent_cleanup_pending_signal_handlers(struct tevent_signal *se)
+{
+	struct tevent_common_signal_list *sl;
+	sl = talloc_get_type(se->additional_data,
+			     struct tevent_common_signal_list);
+
+	tevent_common_signal_list_destructor(sl);
+
+	if (sig_state->sig_handlers[se->signum] == NULL) {
+		if (sig_state->oldact[se->signum]) {
+			sigaction(se->signum, sig_state->oldact[se->signum], NULL);
+			sig_state->oldact[se->signum] = NULL;
+		}
+	}
+	return;
+}