tracing: Remove locking trace_types_lock from tracing_reset_all_online_cpus()
authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>
Wed, 24 Jul 2013 02:21:59 +0000 (22:21 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sun, 4 Aug 2013 08:50:44 +0000 (16:50 +0800)
commitc62771c88704f0814d0fead60eadc0397a5e832f
treeb0d6fedaa94d8f56ff69227236edde8c74ded190
parente55679914313bbfc003dcdf8ff74a16dec2fe24d
tracing: Remove locking trace_types_lock from tracing_reset_all_online_cpus()

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@broadcom.com

Reported-by: Arend van Spril <arend@broadcom.com>
Tested-by: Arend van Spriel <arend@broadcom.com>
Cc: Alexander Z Lam <azl@google.com>
Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/trace/trace.c