Messages in this thread Patch in this message | | | From | Zqiang <> | Subject | [PATCH] rcu: Update rcu_preempt_deferred_qs() comments for no preemptible RCU | Date | Mon, 20 Jun 2022 14:42:24 +0800 |
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For no preemptible RCU, the rcu_preempt_deferred_qs() only report expedited QS state of current CPU, since preemption does not occur in RCU critical sections, there are no tasks insert to leaf rnp blocked-tasks list, that is to say the tasks structure's ->rcu_blocked_node and the leaf rnp structure's ->blkd_tasks are always empty.
Signed-off-by: Zqiang <qiang1.zhang@intel.com> --- kernel/rcu/tree_plugin.h | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index dc78726b993f..99424c2da5db 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -932,10 +932,12 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) return false; } -// Except that we do need to respond to a request by an expedited grace -// period for a quiescent state from this CPU. Note that requests from -// tasks are handled when removing the task from the blocked-tasks list -// below. +/* + * Except that we do need to respond to a request by an expedited grace + * period for a quiescent state from this CPU. Note that for no preemptible + * RCU, since preemption does not occur in RCU critical sections, so the + * leaf rnp's blocked-tasks list is always empty. + */ void rcu_preempt_deferred_qs(struct task_struct *t) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); -- 2.25.1
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