This is a note to let you know that I've just added the patch titled
tracing: Remove locking trace_types_lock from tracing_reset_all_online_cpus()
to the 3.10-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-remove-locking-trace_types_lock-from-tracing_reset_all_online_cpus.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 09d8091c024ec88d1541d93eb8ddb2bd5cf10c39 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Date: Tue, 23 Jul 2013 22:21:59 -0400
Subject: tracing: Remove locking trace_types_lock from tracing_reset_all_online_cpus()
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
commit 09d8091c024ec88d1541d93eb8ddb2bd5cf10c39 upstream.
Commit a82274151af "tracing: Protect ftrace_trace_arrays list in trace_events.c"
added taking the trace_types_lock mutex in trace_events.c as there were
several locations that needed it for protection. Unfortunately, it also
encapsulated a call to tracing_reset_all_online_cpus() which also takes
the trace_types_lock, causing a deadlock.
This happens when a module has tracepoints and has been traced. When the
module is removed, the trace events module notifier will grab the
trace_types_lock, do a bunch of clean ups, and also clears the buffer
by calling tracing_reset_all_online_cpus. This doesn't happen often
which explains why it wasn't caught right away.
Commit a82274151af was marked for stable, which means this must be
sent to stable too.
Link: http://lkml.kernel.org/r/51EEC646.7070306@xxxxxxxxxxxx
Reported-by: Arend van Spril <arend@xxxxxxxxxxxx>
Tested-by: Arend van Spriel <arend@xxxxxxxxxxxx>
Cc: Alexander Z Lam <azl@xxxxxxxxxx>
Cc: Vaibhav Nagarnaik <vnagarnaik@xxxxxxxxxx>
Cc: David Sharp <dhsharp@xxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1163,18 +1163,17 @@ void tracing_reset_current(int cpu)
tracing_reset(&global_trace.trace_buffer, cpu);
}
+/* Must have trace_types_lock held */
void tracing_reset_all_online_cpus(void)
{
struct trace_array *tr;
- mutex_lock(&trace_types_lock);
list_for_each_entry(tr, &ftrace_trace_arrays, list) {
tracing_reset_online_cpus(&tr->trace_buffer);
#ifdef CONFIG_TRACER_MAX_TRACE
tracing_reset_online_cpus(&tr->max_buffer);
#endif
}
- mutex_unlock(&trace_types_lock);
}
#define SAVED_CMDLINES 128
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-3.10/tracing-fix-error-handling-to-ensure-instances-can-always-be-removed.patch
queue-3.10/tracing-remove-locking-trace_types_lock-from-tracing_reset_all_online_cpus.patch
queue-3.10/tracing-kill-the-unbalanced-tr-ref-in-tracing_buffers_open.patch
queue-3.10/tracing-miscellaneous-fixes-for-trace_array-ref-counting.patch
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