r20928: added signal events to lib/events

Jeremy asked for this to allow Samba3 to use the Samba4 events library

see torture/local/event.c for an example
(This used to be commit 7e105482ff9a3da6b4708ff99a64f1881614fc5f)

1 files changed, 153 insertions, 0 deletions

diff --git a/source4/lib/events/events_signal.c b/source4/lib/events/events_signal.c
new file mode 100644
index 0000000000..85b42ae4ab
--- /dev/null
+++ b/source4/lib/events/events_signal.c
@@ -0,0 +1,153 @@
+/* 
+   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 2 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, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "includes.h"
+#include "system/filesys.h"
+#include "system/select.h"
+#include "lib/util/dlinklist.h"
+#include "lib/events/events.h"
+#include "lib/events/events_internal.h"
+
+#define NUM_SIGNALS 64
+
+/*
+  the poor design of signals means that this table must be static global
+*/
+static struct {
+	struct signal_event *sig_handlers[NUM_SIGNALS];
+	uint32_t signal_count[NUM_SIGNALS];
+	uint32_t got_signal;
+	int pipe_hack[2];
+} sig_state;
+
+
+/*
+  signal handler - redirects to registered signals
+*/
+static void signal_handler(int signum)
+{
+	char c = 0;
+	sig_state.signal_count[signum]++;
+	sig_state.got_signal++;
+	/* doesn't matter if this pipe overflows */
+	write(sig_state.pipe_hack[1], &c, 1);
+}
+
+
+/*
+  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) {
+		signal(se->signum, SIG_DFL);
+	}
+	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,
+					    event_signal_handler_t handler, 
+					    void *private_data) 
+{
+	struct signal_event *se;
+
+	if (signum >= NUM_SIGNALS) {
+		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;
+
+	if (sig_state.sig_handlers[signum] == NULL) {
+		signal(signum, signal_handler);
+	}
+
+	DLIST_ADD(sig_state.sig_handlers[signum], se);
+
+	talloc_set_destructor(se, signal_event_destructor);
+
+	if (ev->pipe_fde == NULL) {
+		if (sig_state.pipe_hack[0] == 0 && 
+		    sig_state.pipe_hack[1] == 0) {
+			pipe(sig_state.pipe_hack);
+			set_blocking(sig_state.pipe_hack[0], False);
+			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.got_signal == 0) {
+		return 0;
+	}
+	
+	for (i=0;i<NUM_SIGNALS+1;i++) {
+		uint32_t count = sig_state.signal_count[i];
+		if (count != 0) {
+			struct signal_event *se, *next;
+			for (se=sig_state.sig_handlers[i];se;se=next) {
+				next = se->next;
+				se->handler(ev, se, i, count, se->private_data);
+			}
+			sig_state.signal_count[i] -= count;
+			sig_state.got_signal -= count;
+		}
+	}
+
+	return 1;
+}