Re: [PATCH 9/9] tracing: Remove locking trace_types_lock fromtracing_reset_all_online_cpus()

[Arend van Spriel]

On 07/26/2013 03:03 PM, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)"<rostedt@xxxxxxxxxxx>
>
> 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>

Nasty dutch names, huh. If we ever meet on a summit you may try to 
pronounce it :-) Way easier than Finnish.

Regards,
Arend

> Tested-by: Arend van *Spriel*<arend@xxxxxxxxxxxx>
> Cc: Alexander Z Lam<azl@xxxxxxxxxx>
> Cc: Vaibhav Nagarnaik<vnagarnaik@xxxxxxxxxx>
> Cc: David Sharp<dhsharp@xxxxxxxxxx>
> Cc:stable@xxxxxxxxxxxxxxx  # 3.10
> Signed-off-by: Steven Rostedt<rostedt@xxxxxxxxxxx>
> ---
>   kernel/trace/trace.c |    3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)


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