linux-kernel - Re: [PATCH 9/9] tracing: Remove locking trace_types_lock from tracing_reset_all_online

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Message-ID: <51F2A08B.2090207@broadcom.com>
Date:	Fri, 26 Jul 2013 18:15:07 +0200
From:	"Arend van Spriel" <arend@...adcom.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
cc:	linux-kernel@...r.kernel.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...nel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Alexander Z Lam" <azl@...gle.com>,
	"Vaibhav Nagarnaik" <vnagarnaik@...gle.com>,
	"David Sharp" <dhsharp@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH 9/9] tracing: Remove locking trace_types_lock from
 tracing_reset_all_online_cpus()

On 07/26/2013 03:03 PM, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)"<rostedt@...dmis.org>
>
> 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@...adcom.com>

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@...adcom.com>
> Cc: Alexander Z Lam<azl@...gle.com>
> Cc: Vaibhav Nagarnaik<vnagarnaik@...gle.com>
> Cc: David Sharp<dhsharp@...gle.com>
> Cc:stable@...r.kernel.org  # 3.10
> Signed-off-by: Steven Rostedt<rostedt@...dmis.org>
> ---
>   kernel/trace/trace.c |    3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)


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