Update statedump to 3.17 nsproxy locking

This Linux upstream commit introduces locking strategy back and forth:

commit 728dba3a39c66b3d8ac889ddbe38b5b1c264aec3
Author: Eric W. Biederman <ebiederm@xmission.com>
Date:   Mon Feb 3 19:13:49 2014 -0800

    namespaces: Use task_lock and not rcu to protect nsproxy

Use the task lock starting from kernel 3.17 rather than RCU to access
the task nsproxy.

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

diff --git a/lttng-statedump-impl.c b/lttng-statedump-impl.c
index 17b02faf2be564385ff3c2bd5b7a210ef77988d8..2baa1bea7774317eec6d6fd9dad9b35d1bdb8b80 100644 (file)
--- a/lttng-statedump-impl.c
+++ b/lttng-statedump-impl.c
@@ -390,6 +390,9 @@ int lttng_list_interrupts(struct lttng_session *session)
 }
 #endif
 
+/*
+ * Called with task lock held.
+ */
 static
 void lttng_statedump_process_ns(struct lttng_session *session,
                struct task_struct *p,
@@ -401,8 +404,18 @@ void lttng_statedump_process_ns(struct lttng_session *session,
        struct nsproxy *proxy;
        struct pid_namespace *pid_ns;
 
+       /*
+        * Back and forth on locking strategy within Linux upstream for nsproxy.
+        * See Linux upstream commit 728dba3a39c66b3d8ac889ddbe38b5b1c264aec3
+        * "namespaces: Use task_lock and not rcu to protect nsproxy"
+        * for details.
+        */
+#if (LINUX_VERSION_CODE < KERNEL_VERSION(3,17,0))
        rcu_read_lock();
        proxy = task_nsproxy(p);
+#else /* #if (LINUX_VERSION_CODE < KERNEL_VERSION(3,17,0)) */
+       proxy = p->nsproxy;
+#endif /* #else #if (LINUX_VERSION_CODE < KERNEL_VERSION(3,17,0)) */
        if (proxy) {
                pid_ns = lttng_get_proxy_pid_ns(proxy);
                do {
@@ -414,7 +427,9 @@ void lttng_statedump_process_ns(struct lttng_session *session,
                trace_lttng_statedump_process_state(session,
                        p, type, mode, submode, status, NULL);
        }
+#if (LINUX_VERSION_CODE < KERNEL_VERSION(3,17,0))
        rcu_read_unlock();
+#endif /* #if (LINUX_VERSION_CODE < KERNEL_VERSION(3,17,0)) */
 }
 
 static