From: Joel Fernandes <joel@joelfernandes.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org, Boqun Feng <boqun.feng@gmail.com>,
Byungchul Park <byungchul.park@lge.com>,
Ingo Molnar <mingo@redhat.com>, Julia Cartwright <julia@ni.com>,
linux-kselftest@vger.kernel.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Namhyung Kim <namhyung@kernel.org>,
Thomas Glexiner <tglx@linutronix.de>,
Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: Re: [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU
Date: Wed, 11 Jul 2018 21:28:25 -0700 [thread overview]
Message-ID: <20180712042825.GA154647@joelaf.mtv.corp.google.com> (raw)
In-Reply-To: <20180711232120.5dbfa1c7@vmware.local.home>
On Wed, Jul 11, 2018 at 11:21:20PM -0400, Steven Rostedt wrote:
> On Wed, 11 Jul 2018 13:52:49 -0700
> Joel Fernandes <joel@joelfernandes.org> wrote:
>
> > > #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
> > > extern struct tracepoint __tracepoint_##name; \
> > > static inline void trace_##name(proto) \
> > > { \
> > > if (static_key_false(&__tracepoint_##name.key)) \
> > > __DO_TRACE(&__tracepoint_##name, \
> > > TP_PROTO(data_proto), \
> > > TP_ARGS(data_args), \
> > > TP_CONDITION(cond), 0); \
> > > if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
> > > rcu_read_lock_sched_notrace(); \
> > > rcu_dereference_sched(__tracepoint_##name.funcs);\
> > > rcu_read_unlock_sched_notrace(); \
> > > } \
> > > }
> > >
> > > Because lockdep would only trigger warnings when the tracepoint was
> > > enabled and used in a place it shouldn't be, we added the above
> > > IS_ENABLED(CONFIG_LOCKDEP) part to test regardless if the the
> > > tracepoint was enabled or not. Because we do this, we don't need to
> > > have the test in the __DO_TRACE() code itself. That means we can clean
> > > up the code as per Peter's suggestion.
> >
> > Sounds good, I'm Ok with making this change.
> >
> > Just to clarify, are you proposing to change the rcu_dereference_sched to
> > rcu_dereference_raw in both __DECLARE_TRACE and __DO_TRACE?
>
> No, just in __DO_TRACE(). The rcu_dereference_sched() above in
> __DECLARE_TRACE() in the if (IS_ENABLED(CONFIG_LOCKDEP) block is
> required to show the warnings if trace_##name() is used wrong, and is
> the reason we can use rcu_dereference_raw() in __DO_TRACE() in the
> first place ;-)
>
> This brings up another point. We should probably add to
> __DECLARE_TRACE_RCU() this:
>
> #ifndef MODULE
> #define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \
> static inline void trace_##name##_rcuidle(proto) \
> { \
> if (static_key_false(&__tracepoint_##name.key)) \
> __DO_TRACE(&__tracepoint_##name, \
> TP_PROTO(data_proto), \
> TP_ARGS(data_args), \
> TP_CONDITION(cond), 1); \
> + if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
> + int idx; \
> + idx = srcu_read_lock_notrace(&tracepoint_srcu); \
> + srcu_dereference_notrace(__tracepoint_##name.funcs, \
> + &tracepoint_srcu); \
> + srcu_read_unlock_notrace(&tracepoint_srcu, idx); \
> + } \
> }
> #else
>
>
> So that lockdep works with trace_##name##__rcuidle() when the trace
> event is not enabled.
>
> But that should be a separate patch and not part of this series. I may
> write that up tomorrow.
Yes, that sounds good to me and would be good to add the safe guard there.
But you meant srcu_dereference above, not srcu_dereference_notrace right?
Meanwhile I'll drop that lockdep_recursion tomorrow and run some tests and
see how it behaves with Peter's changes.
thanks!
- Joel
next prev parent reply other threads:[~2018-07-12 4:28 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-28 18:21 [PATCH v9 0/7] Centralize and unify usage of preempt/irq tracepoints Joel Fernandes
2018-06-28 18:21 ` [PATCH v9 1/7] srcu: Add notrace variants of srcu_read_{lock,unlock} Joel Fernandes
2018-06-28 18:21 ` [PATCH v9 2/7] srcu: Add notrace variant of srcu_dereference Joel Fernandes
2018-06-28 18:21 ` [PATCH v9 3/7] trace/irqsoff: Split reset into separate functions Joel Fernandes
2018-06-28 18:21 ` [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU Joel Fernandes
2018-07-11 12:49 ` Peter Zijlstra
2018-07-11 13:00 ` Steven Rostedt
2018-07-11 14:27 ` Paul E. McKenney
2018-07-11 14:46 ` Steven Rostedt
2018-07-11 15:15 ` Paul E. McKenney
2018-07-11 20:56 ` Joel Fernandes
2018-07-12 1:22 ` Steven Rostedt
2018-07-12 2:35 ` Joel Fernandes
2018-07-11 20:52 ` Joel Fernandes
2018-07-12 3:21 ` Steven Rostedt
2018-07-12 4:28 ` Joel Fernandes [this message]
2018-07-12 13:35 ` Steven Rostedt
2018-07-12 19:17 ` Joel Fernandes
2018-07-12 20:15 ` Steven Rostedt
2018-07-12 20:29 ` Joel Fernandes
2018-07-12 20:31 ` Steven Rostedt
2018-07-11 12:53 ` Peter Zijlstra
2018-07-12 2:32 ` Joel Fernandes
2018-07-11 12:56 ` Peter Zijlstra
2018-07-11 13:06 ` Steven Rostedt
2018-07-11 15:17 ` Peter Zijlstra
2018-07-11 15:26 ` Steven Rostedt
2018-07-11 16:46 ` Mathieu Desnoyers
2018-07-11 16:40 ` Mathieu Desnoyers
2018-07-12 0:31 ` Joel Fernandes
2018-07-12 1:26 ` Steven Rostedt
2018-06-28 18:21 ` [PATCH v9 5/7] tracing: Centralize preemptirq tracepoints and unify their usage Joel Fernandes
2018-07-06 22:06 ` Steven Rostedt
2018-07-07 4:20 ` Joel Fernandes
2018-07-10 14:20 ` Steven Rostedt
2018-07-10 17:33 ` Joel Fernandes
2018-07-11 13:12 ` Peter Zijlstra
2018-07-11 13:19 ` Steven Rostedt
2018-07-11 13:22 ` Steven Rostedt
2018-07-12 8:38 ` Joel Fernandes
2018-07-12 13:37 ` Steven Rostedt
2018-07-12 0:44 ` Joel Fernandes
2018-06-28 18:21 ` [PATCH v9 6/7] lib: Add module to simulate atomic sections for testing preemptoff tracers Joel Fernandes
2018-07-11 0:47 ` Steven Rostedt
2018-07-11 5:26 ` Joel Fernandes
2018-06-28 18:21 ` [PATCH v9 7/7] kselftests: Add tests for the preemptoff and irqsoff tracers Joel Fernandes
2018-07-11 0:49 ` Steven Rostedt
2018-07-11 5:27 ` Joel Fernandes
2018-07-03 14:15 ` [PATCH v9 0/7] Centralize and unify usage of preempt/irq tracepoints Joel Fernandes
2018-07-03 14:23 ` Steven Rostedt
-- strict thread matches above, loose matches on Subject: below --
2018-06-21 22:32 Joel Fernandes
2018-06-21 22:32 ` [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU Joel Fernandes
2018-06-07 20:38 [PATCH v9 0/7] Centralize and unify usage of preempt/irq Joel Fernandes
2018-06-07 20:38 ` [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU Joel Fernandes
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