From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 15/17] rcu: Simplify rcu_eqs_{enter,exit}() non-idle task debug code
Date: Fri, 1 Dec 2017 11:36:46 -0800 [thread overview]
Message-ID: <1512157008-22355-15-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <20171201193625.GA20681@linux.vnet.ibm.com>
The code that checks for non-idle non-nohz_idle-usermode tasks invoking
rcu_eqs_enter() and rcu_eqs_exit() prints a considerable quantity of
helpful information. However, these checks fire rarely, so the extra
complexity is no longer worth it. This commit therefore replaces this
debug code with simple WARN_ON_ONCE() statements.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
include/trace/events/rcu.h | 12 +++++-------
kernel/rcu/tree.c | 24 ++----------------------
2 files changed, 7 insertions(+), 29 deletions(-)
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index d103de9f8c10..adf47c635c8e 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -424,15 +424,13 @@ TRACE_EVENT(rcu_fqs,
* as argument: "Start" for entering dyntick-idle mode, "Startirq" for
* entering it from irq/NMI, "End" for leaving it, "Endirq" for leaving it
* to irq/NMI, "--=" for events moving towards idle, and "++=" for events
- * moving away from idle. "Error on entry: not idle task" and "Error
- * on exit: not idle task" indicate that a non-idle task is erroneously
- * toying with the idle loop.
+ * moving away from idle.
*
* These events also take a pair of numbers, which indicate the nesting
- * depth before and after the event of interest. 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.
+ * depth before and after the event of interest, and a third number that is
+ * the ->dynticks 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_dyntick,
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 46a8e06bf03e..4d374d2bc925 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -773,17 +773,7 @@ static void rcu_eqs_enter(bool user)
lockdep_assert_irqs_disabled();
trace_rcu_dyntick(TPS("Start"), rdtp->dynticks_nesting, 0, rdtp->dynticks);
- if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- !user && !is_idle_task(current)) {
- struct task_struct *idle __maybe_unused =
- idle_task(smp_processor_id());
-
- trace_rcu_dyntick(TPS("Error on entry: not idle task"), rdtp->dynticks_nesting, 0, rdtp->dynticks);
- rcu_ftrace_dump(DUMP_ORIG);
- WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
- current->pid, current->comm,
- idle->pid, idle->comm); /* must be idle task! */
- }
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
for_each_rcu_flavor(rsp) {
rdp = this_cpu_ptr(rsp->rda);
do_nocb_deferred_wakeup(rdp);
@@ -941,17 +931,7 @@ static void rcu_eqs_exit(bool user)
rcu_dynticks_eqs_exit();
rcu_cleanup_after_idle();
trace_rcu_dyntick(TPS("End"), rdtp->dynticks_nesting, 1, rdtp->dynticks);
- if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- !user && !is_idle_task(current)) {
- struct task_struct *idle __maybe_unused =
- idle_task(smp_processor_id());
-
- trace_rcu_dyntick(TPS("Error on exit: not idle task"), rdtp->dynticks_nesting, 1, rdtp->dynticks);
- rcu_ftrace_dump(DUMP_ORIG);
- WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
- current->pid, current->comm,
- idle->pid, idle->comm); /* must be idle task! */
- }
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
WRITE_ONCE(rdtp->dynticks_nesting, 1);
WRITE_ONCE(rdtp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
}
--
2.5.2
next prev parent reply other threads:[~2017-12-01 19:39 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-01 19:36 [PATCH tip/core/rcu 0/17] RCU dyntick updates for v4.16 Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 01/17] rcu: Avoid ->dynticks_nmi_nesting store tearing Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 02/17] rcu: Reduce dyntick-idle state space Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 03/17] rcu: Move rcu_nmi_{enter,exit}() to prepare for consolidation Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 04/17] rcu: Clamp ->dynticks_nmi_nesting at eqs entry/exit Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 05/17] rcu: Define rcu_irq_{enter,exit}() in terms of rcu_nmi_{enter,exit}() Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 06/17] rcu: Make ->dynticks_nesting be a simple counter Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 07/17] rcu: Eliminate rcu_irq_enter_disabled() Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 08/17] rcu: Add tracing to irq/NMI dyntick-idle transitions Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 09/17] rcu: Shrink ->dynticks_{nmi_,}nesting from long long to long Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 10/17] rcu: Add ->dynticks field to rcu_dyntick trace event Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 11/17] rcu: Stop duplicating lockdep checks in RCU's idle-entry code Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 12/17] rcu: Avoid ->dynticks_nesting store tearing Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 13/17] rcu: Fold rcu_eqs_enter_common() into rcu_eqs_enter() Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 14/17] rcu: Fold rcu_eqs_exit_common() into rcu_eqs_exit() Paul E. McKenney
2017-12-01 19:36 ` Paul E. McKenney [this message]
2017-12-01 19:36 ` [PATCH tip/core/rcu 16/17] doc: Update dyntick-idle design documentation for NMI/irq consolidation Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 17/17] tracing, rcu: Remove no longer used trace event rcu_prep_idle Paul E. McKenney
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