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Message-ID: <ZjuFUZXk4rYO4L2v@localhost.localdomain>
Date: Wed, 8 May 2024 15:59:45 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Valentin Schneider <vschneid@...hat.com>
Cc: rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
"Paul E. McKenney" <paulmck@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Neeraj Upadhyay <quic_neeraju@...cinc.com>,
Joel Fernandes <joel@...lfernandes.org>,
Josh Triplett <josh@...htriplett.org>,
Boqun Feng <boqun.feng@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Zqiang <qiang.zhang1211@...il.com>
Subject: Re: [PATCH v2 27/27] context_tracking, rcu: Rename rcu_dyntick trace
event into rcu_watching
Le Tue, Apr 30, 2024 at 11:17:31AM +0200, Valentin Schneider a écrit :
> The "rcu_dyntick" naming convention has been turned into "rcu_watching" for
> all helpers now, align the trace event to that.
>
> To add to the confusion, the strings passed to the trace event are now
> reversed: when RCU "starts" the dyntick / EQS state, it "stops" watching.
>
> Signed-off-by: Valentin Schneider <vschneid@...hat.com>
> ---
> include/trace/events/rcu.h | 16 ++++++++--------
> kernel/context_tracking.c | 10 +++++-----
> 2 files changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
> index 4066b6d51e46a..e51ef658437f0 100644
> --- a/include/trace/events/rcu.h
> +++ b/include/trace/events/rcu.h
> @@ -466,40 +466,40 @@ TRACE_EVENT(rcu_stall_warning,
> /*
> * Tracepoint for dyntick-idle entry/exit events. These take 2 strings
> * as argument:
> - * polarity: "Start", "End", "StillNonIdle" for entering, exiting or still not
> + * polarity: "Start", "End", "StillWatching" for entering, exiting or still not
I can't find StillWathing used below.
> * being in dyntick-idle mode.
s/dyntick-idle/eqs
> * context: "USER" or "IDLE" or "IRQ".
> * NMIs nested in IRQs are inferred with nesting > 1 in IRQ context.
> *
> * These events also take a pair of numbers, which indicate the nesting
> * depth before and after the event of interest, and a third number that is
> - * the ->dynticks counter. Note that task-related and interrupt-related
> + * the RCU_WATCHING counter. Note that task-related and interrupt-related
> * events use two separate counters, and that the "++=" and "--=" events
> * for irq/NMI will change the counter by two, otherwise by one.
> */
> -TRACE_EVENT_RCU(rcu_dyntick,
> +TRACE_EVENT_RCU(rcu_watching,
>
> - TP_PROTO(const char *polarity, long oldnesting, long newnesting, int dynticks),
> + TP_PROTO(const char *polarity, long oldnesting, long newnesting, int counter),
>
> - TP_ARGS(polarity, oldnesting, newnesting, dynticks),
> + TP_ARGS(polarity, oldnesting, newnesting, counter),
>
> TP_STRUCT__entry(
> __field(const char *, polarity)
> __field(long, oldnesting)
> __field(long, newnesting)
> - __field(int, dynticks)
> + __field(int, counter)
> ),
>
> TP_fast_assign(
> __entry->polarity = polarity;
> __entry->oldnesting = oldnesting;
> __entry->newnesting = newnesting;
> - __entry->dynticks = dynticks;
> + __entry->counter = counter;
> ),
>
> TP_printk("%s %lx %lx %#3x", __entry->polarity,
> __entry->oldnesting, __entry->newnesting,
> - __entry->dynticks & 0xfff)
> + __entry->counter & 0xfff)
> );
>
> /*
> diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
> index dfa64f21d900d..fdbb584b8e797 100644
> --- a/kernel/context_tracking.c
> +++ b/kernel/context_tracking.c
> @@ -137,7 +137,7 @@ static void noinstr ct_kernel_exit(bool user, int offset)
>
> instrumentation_begin();
> lockdep_assert_irqs_disabled();
> - trace_rcu_dyntick(TPS("Start"), ct_nesting(), 0, ct_rcu_watching());
> + trace_rcu_watching(TPS("End"), ct_nesting(), 0, ct_rcu_watching());
> WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
> rcu_preempt_deferred_qs(current);
>
> @@ -182,7 +182,7 @@ static void noinstr ct_kernel_enter(bool user, int offset)
> // instrumentation for the noinstr ct_kernel_enter_state()
> instrument_atomic_write(&ct->state, sizeof(ct->state));
>
> - trace_rcu_dyntick(TPS("End"), ct_nesting(), 1, ct_rcu_watching());
> + trace_rcu_watching(TPS("Start"), ct_nesting(), 1, ct_rcu_watching());
> WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
> WRITE_ONCE(ct->nesting, 1);
> WARN_ON_ONCE(ct_nmi_nesting());
> @@ -219,7 +219,7 @@ void noinstr ct_nmi_exit(void)
> * leave it in non-RCU-idle state.
> */
> if (ct_nmi_nesting() != 1) {
> - trace_rcu_dyntick(TPS("--="), ct_nmi_nesting(), ct_nmi_nesting() - 2,
> + trace_rcu_watching(TPS("--="), ct_nmi_nesting(), ct_nmi_nesting() - 2,
> ct_rcu_watching());
> WRITE_ONCE(ct->nmi_nesting, /* No store tearing. */
> ct_nmi_nesting() - 2);
> @@ -228,7 +228,7 @@ void noinstr ct_nmi_exit(void)
> }
>
> /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
> - trace_rcu_dyntick(TPS("Startirq"), ct_nmi_nesting(), 0, ct_rcu_watching());
> + trace_rcu_watching(TPS("Endirq"), ct_nmi_nesting(), 0, ct_rcu_watching());
Ah the initial string was wrong and you're fixing it, right?
Should be a seperate patch?
> WRITE_ONCE(ct->nmi_nesting, 0); /* Avoid store tearing. */
>
> // instrumentation for the noinstr ct_kernel_exit_state()
> @@ -294,7 +294,7 @@ void noinstr ct_nmi_enter(void)
> instrumentation_begin();
> }
>
> - trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
> + trace_rcu_watching(incby == 1 ? TPS("Startirq") : TPS("++="),
Ditto?
Thanks.
> ct_nmi_nesting(),
> ct_nmi_nesting() + incby, ct_rcu_watching());
> instrumentation_end();
> --
> 2.43.0
>
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