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SubjectRe: [PATCH rcu 5/7] rcu: Add nocb_cb_kthread check to rcu_is_callbacks_kthread()
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On 6/21/2022 4:15 AM, Paul E. McKenney wrote:
> From: Zqiang <qiang1.zhang@intel.com>
>
> Callbacks are invoked in RCU kthreads when calbacks are offloaded
> (rcu_nocbs boot parameter) or when RCU's softirq handler has been
> offloaded to rcuc kthreads (use_softirq==0). The current code allows
> for the rcu_nocbs case but not the use_softirq case. This commit adds
> support for the use_softirq case.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Zqiang <qiang1.zhang@intel.com>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> ---


Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>


Thanks
Neeraj

> kernel/rcu/tree.c | 4 ++--
> kernel/rcu/tree.h | 2 +-
> kernel/rcu/tree_plugin.h | 33 +++++++++++++++++++--------------
> 3 files changed, 22 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index c25ba442044a6..74455671e6cf2 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2530,7 +2530,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
> trace_rcu_batch_end(rcu_state.name, 0,
> !rcu_segcblist_empty(&rdp->cblist),
> need_resched(), is_idle_task(current),
> - rcu_is_callbacks_kthread());
> + rcu_is_callbacks_kthread(rdp));
> return;
> }
>
> @@ -2608,7 +2608,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
> rcu_nocb_lock_irqsave(rdp, flags);
> rdp->n_cbs_invoked += count;
> trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(),
> - is_idle_task(current), rcu_is_callbacks_kthread());
> + is_idle_task(current), rcu_is_callbacks_kthread(rdp));
>
> /* Update counts and requeue any remaining callbacks. */
> rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
> diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> index 4f8532c33558f..649ad4f0129b1 100644
> --- a/kernel/rcu/tree.h
> +++ b/kernel/rcu/tree.h
> @@ -426,7 +426,7 @@ static void rcu_flavor_sched_clock_irq(int user);
> static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
> static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
> static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
> -static bool rcu_is_callbacks_kthread(void);
> +static bool rcu_is_callbacks_kthread(struct rcu_data *rdp);
> static void rcu_cpu_kthread_setup(unsigned int cpu);
> static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
> static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index c8ba0fe17267c..0483e1338c413 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -1012,6 +1012,25 @@ static void rcu_cpu_kthread_setup(unsigned int cpu)
> WRITE_ONCE(rdp->rcuc_activity, jiffies);
> }
>
> +static bool rcu_is_callbacks_nocb_kthread(struct rcu_data *rdp)
> +{
> +#ifdef CONFIG_RCU_NOCB_CPU
> + return rdp->nocb_cb_kthread == current;
> +#else
> + return false;
> +#endif
> +}
> +
> +/*
> + * Is the current CPU running the RCU-callbacks kthread?
> + * Caller must have preemption disabled.
> + */
> +static bool rcu_is_callbacks_kthread(struct rcu_data *rdp)
> +{
> + return rdp->rcu_cpu_kthread_task == current ||
> + rcu_is_callbacks_nocb_kthread(rdp);
> +}
> +
> #ifdef CONFIG_RCU_BOOST
>
> /*
> @@ -1151,15 +1170,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
> }
> }
>
> -/*
> - * Is the current CPU running the RCU-callbacks kthread?
> - * Caller must have preemption disabled.
> - */
> -static bool rcu_is_callbacks_kthread(void)
> -{
> - return __this_cpu_read(rcu_data.rcu_cpu_kthread_task) == current;
> -}
> -
> #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
>
> /*
> @@ -1242,11 +1252,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
> raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
> }
>
> -static bool rcu_is_callbacks_kthread(void)
> -{
> - return false;
> -}
> -
> static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
> {
> }

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