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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-08-20 18:29:32 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-09-28 21:38:48 -0700 |
| commit | e90c53d3e238dd0b7b02964370e8fece1778df96 (patch) | |
| tree | 23e5b8623c2c37bd8a4656c66266209872f80701 /kernel | |
| parent | 5b61b0baa9e80289c53413e573befc5790a04ac7 (diff) | |
| download | linux-e90c53d3e238dd0b7b02964370e8fece1778df96.tar.bz2 | |
rcu: Remove rcu_needs_cpu_flush() to avoid false quiescent states
The purpose of rcu_needs_cpu_flush() was to iterate on pushing the
current grace period in order to help the current CPU enter dyntick-idle
mode. However, this can result in failures if the CPU starts entering
dyntick-idle mode, but then backs out. In this case, the call to
rcu_pending() from rcu_needs_cpu_flush() might end up announcing a
non-existing quiescent state.
This commit therefore removes rcu_needs_cpu_flush() in favor of letting
the dyntick-idle machinery at the end of the softirq handler push the
loop along via its call to rcu_pending().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcutree.c | 3 | ||||
| -rw-r--r-- | kernel/rcutree.h | 1 | ||||
| -rw-r--r-- | kernel/rcutree_plugin.h | 25 |
3 files changed, 0 insertions, 29 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 8455043c9250..e75df0c93abd 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1528,9 +1528,6 @@ static void rcu_process_callbacks(struct softirq_action *unused) &__get_cpu_var(rcu_sched_data)); __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); rcu_preempt_process_callbacks(); - - /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ - rcu_needs_cpu_flush(); trace_rcu_utilization("End RCU core"); } diff --git a/kernel/rcutree.h b/kernel/rcutree.h index f509f728f9fb..849ce9ec51fe 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -458,7 +458,6 @@ static int rcu_preempt_needs_cpu(int cpu); static void __cpuinit rcu_preempt_init_percpu_data(int cpu); static void rcu_preempt_send_cbs_to_online(void); static void __init __rcu_init_preempt(void); -static void rcu_needs_cpu_flush(void); static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); static void invoke_rcu_callbacks_kthread(void); diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index b4cbe5bf2326..4b9b9f8a4184 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1948,15 +1948,6 @@ int rcu_needs_cpu(int cpu) return rcu_needs_cpu_quick_check(cpu); } -/* - * Check to see if we need to continue a callback-flush operations to - * allow the last CPU to enter dyntick-idle mode. But fast dyntick-idle - * entry is not configured, so we never do need to. - */ -static void rcu_needs_cpu_flush(void) -{ -} - #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ #define RCU_NEEDS_CPU_FLUSHES 5 @@ -2032,20 +2023,4 @@ int rcu_needs_cpu(int cpu) return c; } -/* - * Check to see if we need to continue a callback-flush operations to - * allow the last CPU to enter dyntick-idle mode. - */ -static void rcu_needs_cpu_flush(void) -{ - int cpu = smp_processor_id(); - unsigned long flags; - - if (per_cpu(rcu_dyntick_drain, cpu) <= 0) - return; - local_irq_save(flags); - (void)rcu_needs_cpu(cpu); - local_irq_restore(flags); -} - #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |