Commit-ID: a0eb22bf64a755bb162b421120b9fbe7d012b85f
Gitweb: https://git.kernel.org/tip/a0eb22bf64a755bb162b421120b9fbe7d012b85f
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 2 Oct 2017 19:45:10 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 27 Nov 2017 08:40:10 -0800
rcu: Reduce dyntick-idle state space
Both extended-quiescent-state entry and exit first update the nesting
counter and then adjust the dyntick-idle state. This means that there
are four states: (1) Both nesting and dyntick idle indicate idle,
(2) Nesting indicates idle but dyntick idle does not, (3) Nesting indicates
non-idle and dyntick idle does not, and (4) Both nesting and dyntick
idle indicate non-idle. This commit simplifies the state space by
eliminating #3, reversing the order of updates on exit from extended
quiescent state.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c5d960f..49f661b 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -928,21 +928,21 @@ void rcu_irq_exit_irqson(void)
* we really have exited idle, and must do the appropriate accounting.
* The caller must have disabled interrupts.
*/
-static void rcu_eqs_exit_common(long long oldval, int user)
+static void rcu_eqs_exit_common(long long newval, int user)
{
RCU_TRACE(struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);)
rcu_dynticks_task_exit();
rcu_dynticks_eqs_exit();
rcu_cleanup_after_idle();
- trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
+ trace_rcu_dyntick(TPS("End"), rdtp->dynticks_nesting, newval);
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"),
- oldval, rdtp->dynticks_nesting);
+ rdtp->dynticks_nesting, newval);
rcu_ftrace_dump(DUMP_ORIG);
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
current->pid, current->comm,
@@ -967,8 +967,8 @@ static void rcu_eqs_exit(bool user)
rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
} else {
__this_cpu_inc(disable_rcu_irq_enter);
+ rcu_eqs_exit_common(DYNTICK_TASK_EXIT_IDLE, user);
rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
- rcu_eqs_exit_common(oldval, user);
__this_cpu_dec(disable_rcu_irq_enter);
}
}
@@ -1037,7 +1037,7 @@ void rcu_user_exit(void)
void rcu_irq_enter(void)
{
struct rcu_dynticks *rdtp;
- long long oldval;
+ long long newval;
lockdep_assert_irqs_disabled();
rdtp = this_cpu_ptr(&rcu_dynticks);
@@ -1046,14 +1046,13 @@ void rcu_irq_enter(void)
if (rdtp->dynticks_nmi_nesting)
return;
- oldval = rdtp->dynticks_nesting;
- rdtp->dynticks_nesting++;
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- rdtp->dynticks_nesting == 0);
- if (oldval)
- trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting);
+ newval = rdtp->dynticks_nesting + 1;
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && newval == 0);
+ if (rdtp->dynticks_nesting)
+ trace_rcu_dyntick(TPS("++="), rdtp->dynticks_nesting, newval);
else
- rcu_eqs_exit_common(oldval, true);
+ rcu_eqs_exit_common(newval, true);
+ rdtp->dynticks_nesting++;
}
/*
--
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