# HG changeset patch
# User emellor@xxxxxxxxxxxxxxxxxxxxxx
# Node ID 975aa9e4def35fa8059755129f03f078677355b6
# Parent 4982559d8fde3d0a4401766deb54c5cc1e1a0ec5
Fix the log reopening by moving the code with all the races out of the signal
handler and into the main loop. The "self-pipe trick" is used to awaken the
select() call on SIGHUP.
Signed-off-by: Ewan Mellor <ewan@xxxxxxxxxxxxx>
diff -r 4982559d8fde -r 975aa9e4def3 tools/xenstore/xenstored_core.c
--- a/tools/xenstore/xenstored_core.c Thu Nov 10 14:16:01 2005
+++ b/tools/xenstore/xenstored_core.c Thu Nov 10 15:20:27 2005
@@ -56,6 +56,7 @@
static bool verbose;
LIST_HEAD(connections);
static int tracefd = -1;
+static int reopen_log_pipe[2];
static char *tracefile = NULL;
static TDB_CONTEXT *tdb_ctx;
@@ -243,20 +244,34 @@
talloc_free(str);
}
-void reopen_log()
-{
- if (!tracefile)
- return;
-
- if (tracefd > 0)
- close(tracefd);
- tracefd = open(tracefile, O_WRONLY|O_CREAT|O_APPEND, 0600);
- if (tracefd < 0) {
- perror("Could not open tracefile");
- return;
- }
- write(tracefd, "\n***\n", strlen("\n***\n"));
-}
+
+/**
+ * Signal handler for SIGHUP, which requests that the trace log is reopened
+ * (in the main loop). A single byte is written to reopen_log_pipe, to awaken
+ * the select() in the main loop.
+ */
+static void trigger_reopen_log(int signal __attribute__((unused)))
+{
+ char c = 'A';
+ write(reopen_log_pipe[1], &c, 1);
+}
+
+
+static void reopen_log()
+{
+ if (tracefile) {
+ if (tracefd > 0)
+ close(tracefd);
+
+ tracefd = open(tracefile, O_WRONLY|O_CREAT|O_APPEND, 0600);
+
+ if (tracefd < 0)
+ perror("Could not open tracefile");
+ else
+ write(tracefd, "\n***\n", strlen("\n***\n"));
+ }
+}
+
static bool write_messages(struct connection *conn)
{
@@ -331,29 +346,33 @@
return 0;
}
+
+static void set_fd(int fd, fd_set *set, int *max)
+{
+ FD_SET(fd, set);
+ if (fd > *max)
+ *max = fd;
+}
+
+
static int initialize_set(fd_set *inset, fd_set *outset, int sock, int ro_sock)
{
struct connection *i;
- int max;
+ int max = -1;
FD_ZERO(inset);
FD_ZERO(outset);
- FD_SET(sock, inset);
- max = sock;
- FD_SET(ro_sock, inset);
- if (ro_sock > max)
- max = ro_sock;
- FD_SET(eventchn_fd, inset);
- if (eventchn_fd > max)
- max = eventchn_fd;
+
+ set_fd(sock, inset, &max);
+ set_fd(ro_sock, inset, &max);
+ set_fd(eventchn_fd, inset, &max);
+ set_fd(reopen_log_pipe[0], inset, &max);
list_for_each_entry(i, &connections, list) {
if (i->domain)
continue;
- FD_SET(i->fd, inset);
+ set_fd(i->fd, inset, &max);
if (!list_empty(&i->out_list))
FD_SET(i->fd, outset);
- if (i->fd > max)
- max = i->fd;
}
return max;
}
@@ -1570,6 +1589,10 @@
|| listen(*ro_sock, 1) != 0)
barf_perror("Could not listen on sockets");
+ if (pipe(reopen_log_pipe)) {
+ barf_perror("pipe");
+ }
+
/* Setup the database */
setup_structure();
@@ -1592,7 +1615,7 @@
close(STDERR_FILENO);
}
- signal(SIGHUP, reopen_log);
+ signal(SIGHUP, trigger_reopen_log);
#ifdef TESTING
signal(SIGUSR1, stop_failtest);
@@ -1610,6 +1633,12 @@
if (errno == EINTR)
continue;
barf_perror("Select failed");
+ }
+
+ if (FD_ISSET(reopen_log_pipe[0], &inset)) {
+ char c;
+ read(reopen_log_pipe[0], &c, 1);
+ reopen_log();
}
if (FD_ISSET(*sock, &inset))
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