Commit 740466bc authored Mar 13, 2013 by Steven Rostedt (Red Hat) Committed by Steven Rostedt Mar 13, 2013

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



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().

Cc: stable@vger.kernel.org
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent 2721e72d

kernel/trace/ftrace.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3108,8 +3108,8 @@ __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();

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