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| author |   Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-10-02 19:45:10 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-11-27 08:40:10 -0800 |
| commit | a0eb22bf64a755bb162b421120b9fbe7d012b85f (patch) | |
| tree | 6bfe025b6e0003e660dd79e1f6a83b80ec125ad0 /kernel/rcu | |
| parent | rcu: Avoid ->dynticks_nmi_nesting store tearing (diff) | |
| download | linux-dev-a0eb22bf64a755bb162b421120b9fbe7d012b85f.tar.xz linux-dev-a0eb22bf64a755bb162b421120b9fbe7d012b85f.zip | |
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@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 23 |
1 files changed, 11 insertions, 12 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index c5d960f86cf8..49f661bb8ffe 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++; } /* |