[PATCH] xenstore: add memory allocation debugging capability

[Juergen Gross <jgross@suse.com>]

Add support for debugging memory allocation statistics to xenstored.
Specifying "-M <file>" on the command line will enable the feature.
Whenever xenstored receives SIGUSR1 it will dump out a full talloc
report to <file>. This helps finding e.g. memory leaks in xenstored.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
To be applied on top of my "xenstore: fix memory leak of xenstored"
series. In fact this patch was used to find the problem the series
fixed and I used it to verify the patches are working.
---
 tools/xenstore/xenstored_core.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 8cb12c7..ab737eb 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -71,6 +71,7 @@ static int reopen_log_pipe[2];
 static int reopen_log_pipe0_pollfd_idx = -1;
 static char *tracefile = NULL;
 static TDB_CONTEXT *tdb_ctx = NULL;
+static bool trigger_talloc_report = false;
 
 static void corrupt(struct connection *conn, const char *fmt, ...);
 static void check_store(void);
@@ -1743,6 +1744,10 @@ static void init_sockets(int **psock, int **pro_sock)
 	static int minus_one = -1;
 	*psock = *pro_sock = &minus_one;
 }
+
+static void do_talloc_report(int sig)
+{
+}
 #else
 static int destroy_fd(void *_fd)
 {
@@ -1798,6 +1803,11 @@ static void init_sockets(int **psock, int **pro_sock)
 
 
 }
+
+static void do_talloc_report(int sig)
+{
+	trigger_talloc_report = true;
+}
 #endif
 
 static void usage(void)
@@ -1823,6 +1833,7 @@ static void usage(void)
 "                          the store is corrupted (debug only),\n"
 "  -I, --internal-db       store database in memory, not on disk\n"
 "  -L, --preserve-local    to request that /local is preserved on start-up,\n"
+"  -M, --memory-debug <file>  support memory debugging to file,\n"
 "  -V, --verbose           to request verbose execution.\n");
 }
 
@@ -1845,6 +1856,7 @@ static struct option options[] = {
 	{ "internal-db", 0, NULL, 'I' },
 	{ "verbose", 0, NULL, 'V' },
 	{ "watch-nb", 1, NULL, 'W' },
+	{ "memory-debug", 1, NULL, 'M' },
 	{ NULL, 0, NULL, 0 } };
 
 extern void dump_conn(struct connection *conn); 
@@ -1860,9 +1872,10 @@ int main(int argc, char *argv[])
 	bool outputpid = false;
 	bool no_domain_init = false;
 	const char *pidfile = NULL;
+	const char *memfile = NULL;
 	int timeout;
 
-	while ((opt = getopt_long(argc, argv, "DE:F:HNPS:t:T:RLVW:", options,
+	while ((opt = getopt_long(argc, argv, "DE:F:HNPS:t:T:RLVW:M:", options,
 				  NULL)) != -1) {
 		switch (opt) {
 		case 'D':
@@ -1916,6 +1929,9 @@ int main(int argc, char *argv[])
 		case 'p':
 			priv_domid = strtol(optarg, NULL, 10);
 			break;
+		case 'M':
+			memfile = optarg;
+			break;
 		}
 	}
 	if (optind != argc)
@@ -1942,6 +1958,11 @@ int main(int argc, char *argv[])
 	/* Don't kill us with SIGPIPE. */
 	signal(SIGPIPE, SIG_IGN);
 
+	if (memfile) {
+		talloc_enable_null_tracking();
+		signal(SIGUSR1, do_talloc_report);
+	}
+
 	init_sockets(&sock, &ro_sock);
 
 	init_pipe(reopen_log_pipe);
@@ -1978,6 +1999,17 @@ int main(int argc, char *argv[])
 	for (;;) {
 		struct connection *conn, *next;
 
+		if (trigger_talloc_report) {
+			FILE *out;
+
+			trigger_talloc_report = false;
+			out = fopen(memfile, "a");
+			if (out) {
+				talloc_report_full(NULL, out);
+				fclose(out);
+			}
+		}
+
 		if (poll(fds, nr_fds, timeout) < 0) {
 			if (errno == EINTR)
 				continue;
-- 
2.6.6


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