From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Dave Hansen <dave@sr71.net>, Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH 08/11] tracing: generate RCU warnings even when tracepoints are disabled
Date: Mon, 6 Oct 2014 19:39:53 -0700 [thread overview]
Message-ID: <20141007023953.GA5015@linux.vnet.ibm.com> (raw)
In-Reply-To: <20141006213631.352752419@goodmis.org>
On Mon, Oct 06, 2014 at 05:35:52PM -0400, Steven Rostedt wrote:
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> Dave Jones reported seeing a bug from one of my TLB tracepoints:
>
> http://lkml.kernel.org/r/20140806181801.GA4605@redhat.com
>
> I've been running these patches for months and never saw this.
> But, a big chunk of my testing, especially with all the debugging
> enabled, was in a vm where intel_idle doesn't work. On the
> systems where I was using intel_idle, I never had lockdep enabled
> and this tracepoint on at the same time.
>
> This patch ensures that whenever we have lockdep available, we do
> _some_ RCU activity at the site of the tracepoint, despite
> whether the tracepoint's condition matches or even if the
> tracepoint itself is completely disabled. This is a bit of a
> hack, but it is pretty self-contained.
>
> I confirmed that with this patch plus lockdep I get the same
> splat as Dave Jones did, but without enabling the tracepoint
> explicitly.
>
> Link: http://lkml.kernel.org/p/20140807175204.C257CAC5@viggo.jf.intel.com
>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Dave Hansen <dave@sr71.net>
> Cc: Dave Jones <davej@redhat.com>,
> Cc: paulmck@linux.vnet.ibm.com
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> include/linux/tracepoint.h | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index b1293f15f592..e08e21e5f601 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -157,6 +157,12 @@ extern void syscall_unregfunc(void);
> * Make sure the alignment of the structure in the __tracepoints section will
> * not add unwanted padding between the beginning of the section and the
> * structure. Force alignment to the same alignment as the section start.
> + *
> + * When lockdep is enabled, we make sure to always do the RCU portions of
> + * the tracepoint code, regardless of whether tracing is on or we match the
> + * condition. This lets us find RCU issues triggered with tracepoints even
> + * when this tracepoint is off. This code has no purpose other than poking
> + * RCU a bit.
> */
> #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
> extern struct tracepoint __tracepoint_##name; \
> @@ -167,6 +173,11 @@ extern void syscall_unregfunc(void);
> TP_PROTO(data_proto), \
> TP_ARGS(data_args), \
> TP_CONDITION(cond),,); \
> + if (IS_ENABLED(CONFIG_LOCKDEP)) { \
> + rcu_read_lock_sched_notrace(); \
> + rcu_dereference_sched(__tracepoint_##name.funcs);\
> + rcu_read_unlock_sched_notrace(); \
> + } \
> } \
> __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args), \
> PARAMS(cond), PARAMS(data_proto), PARAMS(data_args)) \
> --
> 2.0.1
>
>
next prev parent reply other threads:[~2014-10-07 2:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-06 21:35 [PATCH 00/11] [GIT PULL] tracing: Updates for 3.18 Steven Rostedt
2014-10-06 21:35 ` [PATCH 01/11] ftrace: Add separate function for non recursive callbacks Steven Rostedt
2014-10-06 21:35 ` [PATCH 02/11] ftrace: Add helper function ftrace_ops_get_func() Steven Rostedt
2014-10-06 21:35 ` [PATCH 03/11] ftrace: Set callback to ftrace_stub when no ops are registered Steven Rostedt
2014-10-06 21:35 ` [PATCH 04/11] ftrace: Remove freeing of old_hash from ftrace_hash_move() Steven Rostedt
2014-10-06 21:35 ` [PATCH 05/11] ftrace: Grab any ops for a rec for enabled_functions output Steven Rostedt
2014-10-06 21:35 ` [PATCH 06/11] ftrace: Annotate the ops operation on update Steven Rostedt
2014-10-06 21:35 ` [PATCH 07/11] ftrace: Replace tramp_hash with old_*_hash to save space Steven Rostedt
2014-10-06 21:35 ` [PATCH 08/11] tracing: generate RCU warnings even when tracepoints are disabled Steven Rostedt
2014-10-07 2:39 ` Paul E. McKenney [this message]
2014-10-06 21:35 ` [PATCH 09/11] kernel: trace_syscalls: Replace rcu_assign_pointer() with RCU_INIT_POINTER() Steven Rostedt
2014-10-06 21:35 ` [PATCH 10/11] ftrace: Add sanity check when unregistering last ftrace_ops Steven Rostedt
2014-10-06 21:35 ` [PATCH 11/11] ftrace: Only disable ftrace_enabled to test buffer in selftest Steven Rostedt
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