diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2011-10-05 11:59:38 -0700 |
---|---|---|
committer | Anders Roxell <anders.roxell@linaro.org> | 2015-07-26 11:08:21 +0200 |
commit | 0e8f25a5c4642d14898e1309c083fac1b5df130b (patch) | |
tree | e839109cd81e434d1768e30e132bc07d4ee22463 /kernel/rcu | |
parent | e01a1d9d8cd454c4e7c9ddc1ca639146e3f5383b (diff) |
rcu: Merge RCU-bh into RCU-preempt
The Linux kernel has long RCU-bh read-side critical sections that
intolerably increase scheduling latency under mainline's RCU-bh rules,
which include RCU-bh read-side critical sections being non-preemptible.
This patch therefore arranges for RCU-bh to be implemented in terms of
RCU-preempt for CONFIG_PREEMPT_RT_FULL=y.
This has the downside of defeating the purpose of RCU-bh, namely,
handling the case where the system is subjected to a network-based
denial-of-service attack that keeps at least one CPU doing full-time
softirq processing. This issue will be fixed by a later commit.
The current commit will need some work to make it appropriate for
mainline use, for example, it needs to be extended to cover Tiny RCU.
[ paulmck: Added a useful changelog ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20111005185938.GA20403@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/rcu')
-rw-r--r-- | kernel/rcu/tree.c | 16 | ||||
-rw-r--r-- | kernel/rcu/update.c | 2 |
2 files changed, 18 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8cf7304b2867..65aecd8681c2 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -220,6 +220,7 @@ void rcu_sched_qs(void) } } +#ifndef CONFIG_PREEMPT_RT_FULL void rcu_bh_qs(void) { if (!__this_cpu_read(rcu_bh_data.passed_quiesce)) { @@ -229,6 +230,7 @@ void rcu_bh_qs(void) __this_cpu_write(rcu_bh_data.passed_quiesce, 1); } } +#endif static DEFINE_PER_CPU(int, rcu_sched_qs_mask); @@ -404,6 +406,7 @@ unsigned long rcu_batches_completed_sched(void) } EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); +#ifndef CONFIG_PREEMPT_RT_FULL /* * Return the number of RCU BH batches completed thus far for debug & stats. */ @@ -431,6 +434,13 @@ void rcu_bh_force_quiescent_state(void) } EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); +#else +void rcu_force_quiescent_state(void) +{ +} +EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); +#endif + /* * Force a quiescent state for RCU-sched. */ @@ -3040,6 +3050,7 @@ void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) } EXPORT_SYMBOL_GPL(call_rcu_sched); +#ifndef CONFIG_PREEMPT_RT_FULL /* * Queue an RCU callback for invocation after a quicker grace period. */ @@ -3048,6 +3059,7 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) __call_rcu(head, func, &rcu_bh_state, -1, 0); } EXPORT_SYMBOL_GPL(call_rcu_bh); +#endif /* * Queue an RCU callback for lazy invocation after a grace period. @@ -3139,6 +3151,7 @@ void synchronize_sched(void) } EXPORT_SYMBOL_GPL(synchronize_sched); +#ifndef CONFIG_PREEMPT_RT_FULL /** * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. * @@ -3165,6 +3178,7 @@ void synchronize_rcu_bh(void) wait_rcu_gp(call_rcu_bh); } EXPORT_SYMBOL_GPL(synchronize_rcu_bh); +#endif /** * get_state_synchronize_rcu - Snapshot current RCU state @@ -3677,6 +3691,7 @@ static void _rcu_barrier(struct rcu_state *rsp) mutex_unlock(&rsp->barrier_mutex); } +#ifndef CONFIG_PREEMPT_RT_FULL /** * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. */ @@ -3685,6 +3700,7 @@ void rcu_barrier_bh(void) _rcu_barrier(&rcu_bh_state); } EXPORT_SYMBOL_GPL(rcu_barrier_bh); +#endif /** * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 1f133350da01..1718c4fe9bce 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -227,6 +227,7 @@ int rcu_read_lock_held(void) } EXPORT_SYMBOL_GPL(rcu_read_lock_held); +#ifndef CONFIG_PREEMPT_RT_FULL /** * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? * @@ -253,6 +254,7 @@ int rcu_read_lock_bh_held(void) return in_softirq() || irqs_disabled(); } EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); +#endif #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |