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SubjectRe: [PATCH 3/5] Add rcu_barrier_sched() and rcu_barrier_bh()
On Mon, Apr 21, 2008 at 05:47:43PM -0700, Paul E. McKenney wrote:
> Add rcu_barrier_sched() and rcu_barrier_bh(). With these in place,
> rcutorture no longer gives the occasional oops when repeatedly starting
> and stopping torturing rcu_bh. Also adds the API needed to flush out
> pre-existing call_rcu_sched() callbacks.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> ---
>
> include/linux/rcupdate.h | 2 +
> kernel/rcupdate.c | 55 +++++++++++++++++++++++++++++++++++++++++------
> 2 files changed, 51 insertions(+), 6 deletions(-)
>
> diff -urpNa -X dontdiff linux-2.6.25-C2-rcuclassic-fixes/include/linux/rcupdate.h linux-2.6.25-C3-rcu_barrier_sched/include/linux/rcupdate.h
> --- linux-2.6.25-C2-rcuclassic-fixes/include/linux/rcupdate.h 2008-04-17 08:10:33.000000000 -0700
> +++ linux-2.6.25-C3-rcu_barrier_sched/include/linux/rcupdate.h 2008-04-21 11:33:07.000000000 -0700
> @@ -260,6 +260,8 @@ extern void call_rcu_bh(struct rcu_head
> /* Exported common interfaces */
> extern void synchronize_rcu(void);
> extern void rcu_barrier(void);
> +extern void rcu_barrier_bh(void);
> +extern void rcu_barrier_sched(void);
> extern long rcu_batches_completed(void);
> extern long rcu_batches_completed_bh(void);
>
> diff -urpNa -X dontdiff linux-2.6.25-C2-rcuclassic-fixes/kernel/rcupdate.c linux-2.6.25-C3-rcu_barrier_sched/kernel/rcupdate.c
> --- linux-2.6.25-C2-rcuclassic-fixes/kernel/rcupdate.c 2008-04-17 08:10:33.000000000 -0700
> +++ linux-2.6.25-C3-rcu_barrier_sched/kernel/rcupdate.c 2008-04-21 11:33:08.000000000 -0700
> @@ -45,6 +45,12 @@
> #include <linux/mutex.h>
> #include <linux/module.h>
>
> +enum rcu_barrier {
> + RCU_BARRIER_STD,
STD: Standard, I take it ?

> + RCU_BARRIER_BH,
> + RCU_BARRIER_SCHED,
> +};
> +
> static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
> static atomic_t rcu_barrier_cpu_count;
> static DEFINE_MUTEX(rcu_barrier_mutex);
> @@ -83,19 +89,30 @@ static void rcu_barrier_callback(struct
> /*
> * Called with preemption disabled, and from cross-cpu IRQ context.
> */
> -static void rcu_barrier_func(void *notused)
> +static void rcu_barrier_func(void *type)
> {
> int cpu = smp_processor_id();
> struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
>
> atomic_inc(&rcu_barrier_cpu_count);
> - call_rcu(head, rcu_barrier_callback);
> + switch ((enum rcu_barrier)type) {
> + case RCU_BARRIER_STD:
> + call_rcu(head, rcu_barrier_callback);
> + break;
> + case RCU_BARRIER_BH:
> + call_rcu_bh(head, rcu_barrier_callback);
> + break;
> + case RCU_BARRIER_SCHED:
> + call_rcu_sched(head, rcu_barrier_callback);
> + break;
> + }
> }
>
> -/**
> - * rcu_barrier - Wait until all the in-flight RCUs are complete.
> +/*
> + * Orchestrate the specified type of RCU barrier, waiting for all
> + * RCU callbacks of the specified type to complete.
> */
> -void rcu_barrier(void)
> +static void _rcu_barrier(enum rcu_barrier type)
> {
> BUG_ON(in_interrupt());
> /* Take cpucontrol mutex to protect against CPU hotplug */
> @@ -111,13 +128,39 @@ void rcu_barrier(void)
> * until all the callbacks are queued.
> */
> rcu_read_lock();
> - on_each_cpu(rcu_barrier_func, NULL, 0, 1);
> + on_each_cpu(rcu_barrier_func, (void *)type, 0, 1);
> rcu_read_unlock();
> wait_for_completion(&rcu_barrier_completion);
> mutex_unlock(&rcu_barrier_mutex);
> }
> +
> +/**
> + * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
> + */
> +void rcu_barrier(void)
> +{
> + _rcu_barrier(RCU_BARRIER_STD);
> +}
> EXPORT_SYMBOL_GPL(rcu_barrier);
>
> +/**
> + * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
> + */
> +void rcu_barrier_bh(void)
> +{
> + _rcu_barrier(RCU_BARRIER_BH);
> +}
> +EXPORT_SYMBOL_GPL(rcu_barrier_bh);
> +
> +/**
> + * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
> + */
> +void rcu_barrier_sched(void)
> +{
> + _rcu_barrier(RCU_BARRIER_SCHED);
> +}
> +EXPORT_SYMBOL_GPL(rcu_barrier_sched);
> +
> void __init rcu_init(void)
> {
> __rcu_init();

--
Thanks and Regards
gautham


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