This is a note to let you know that I've just added the patch titled
tracing: Fix free of probe entry by calling call_rcu_sched()
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-fix-free-of-probe-entry-by-calling-call_rcu_sched.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 740466bc89ad8bd5afcc8de220f715f62b21e365 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Date: Wed, 13 Mar 2013 11:15:19 -0400
Subject: tracing: Fix free of probe entry by calling call_rcu_sched()
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
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@xxxxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/ftrace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3034,8 +3034,8 @@ __unregister_ftrace_function_probe(char
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();
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-3.4/tracing-fix-free-of-probe-entry-by-calling-call_rcu_sched.patch
queue-3.4/tracing-fix-race-in-snapshot-swapping.patch
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