From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Mon, 27 Aug 2012 13:46:48 +0000 (-0400)
Subject: Cleanup: no need to hold RCU read-side lock when reading current nsproxy
X-Git-Tag: v2.1.0-rc1~4
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=3d0d43dbac505d33994f5a57f4f11021410fa417;p=lttng-modules.git

Cleanup: no need to hold RCU read-side lock when reading current nsproxy

As documented in include/linux/nsproxy.h.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/lttng-context-hostname.c b/lttng-context-hostname.c
index e38340b7..6dc14f9c 100644
--- a/lttng-context-hostname.c
+++ b/lttng-context-hostname.c
@@ -49,8 +49,11 @@ void hostname_record(struct lttng_ctx_field *field,
 	struct uts_namespace *ns;
 	char *hostname;
 
-	rcu_read_lock();
-	nsproxy = task_nsproxy(current);
+	/*
+	 * No need to take the RCU read-side lock to read current
+	 * nsproxy. (documented in nsproxy.h)
+	 */
+	nsproxy = current->nsproxy;
 	if (nsproxy) {
 		ns = nsproxy->uts_ns;
 		hostname = ns->name.nodename;
@@ -60,7 +63,6 @@ void hostname_record(struct lttng_ctx_field *field,
 		chan->ops->event_memset(ctx, 0,
 				LTTNG_HOSTNAME_CTX_LEN);
 	}
-	rcu_read_unlock();
 }
 
 int lttng_add_hostname_to_ctx(struct lttng_ctx **ctx)
diff --git a/lttng-events.c b/lttng-events.c
index 7a1be729..220178f7 100644
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -903,7 +903,6 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
 	unsigned char uuid_s[37], clock_uuid_s[BOOT_ID_LEN];
 	struct lttng_channel *chan;
 	struct lttng_event *event;
-	char hostname[__NEW_UTS_LEN + 1];
 	int ret = 0;
 
 	if (!ACCESS_ONCE(session->active))
@@ -960,11 +959,6 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
 	if (ret)
 		goto end;
 
-	rcu_read_lock();
-	memcpy(hostname, task_nsproxy(current)->uts_ns->name.nodename,
-		sizeof(hostname));
-	rcu_read_unlock();
-
 	ret = lttng_metadata_printf(session,
 		"env {\n"
 		"	hostname = \"%s\";\n"
@@ -977,7 +971,7 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
 		"	tracer_minor = %d;\n"
 		"	tracer_patchlevel = %d;\n"
 		"};\n\n",
-		hostname,
+		current->nsproxy->uts_ns->name.nodename,
 		utsname()->sysname,
 		utsname()->release,
 		utsname()->version,