tracing: Fix free of probe entry by calling call_rcu_sched()

commit 740466bc89ad8bd5afcc8de220f715f62b21e365 upstream.

Because function tracing is very invasive, and can even trace
calls to rcu_read_lock(), RCU access in function tracing is done
with preempt_disable_notrace(). This requires a synchronize_sched()
for updates and not a synchronize_rcu().

Function probes (traceon, traceoff, etc) must be freed after
a synchronize_sched() after its entry has been removed from the
hash. But call_rcu() is used. Fix this by using call_rcu_sched().

Also fix the usage to use hlist_del_rcu() instead of hlist_del().

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4a86e6404085c68c90a0cc26ab92cc4fb761eeea..62f3751816c8bd50f1e45cfa08afe2c6851d8dbc 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3034,8 +3034,8 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                                        continue;
                        }
 
-                       hlist_del(&entry->node);
-                       call_rcu(&entry->rcu, ftrace_free_entry_rcu);
+                       hlist_del_rcu(&entry->node);
+                       call_rcu_sched(&entry->rcu, ftrace_free_entry_rcu);
                }
        }
        __disable_ftrace_function_probe();