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From:   paulmck@kernel.org
To:     rcu@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org,
        jiangshanlai@gmail.com, dipankar@in.ibm.com,
        akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
        josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
        rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
        fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
        "Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH v3 tip/core/rcu 21/34] rcu-tasks: Add a grace-period start time for throttling and debug
Date:   Fri, 27 Mar 2020 15:24:43 -0700
Message-Id: <20200327222456.12470-21-paulmck@kernel.org>
In-Reply-To: <20200327222346.GA12082@paulmck-ThinkPad-P72>
References: <20200327222346.GA12082@paulmck-ThinkPad-P72>
Sender: linux-kernel-owner@vger.kernel.org
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From: "Paul E. McKenney" <paulmck@kernel.org>

This commit adds a place to record the grace-period start in jiffies.
This will be used by later commits for debugging purposes and to throttle
IPIs early in the grace period.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tasks.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index cbc9905..fa9c069 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -46,6 +46,7 @@ struct rcu_tasks {
 	raw_spinlock_t cbs_lock;
 	int gp_state;
 	unsigned long gp_jiffies;
+	unsigned long gp_start;
 	struct task_struct *kthread_ptr;
 	rcu_tasks_gp_func_t gp_func;
 	pregp_func_t pregp_func;
@@ -200,6 +201,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 
 		// Wait for one grace period.
 		set_tasks_gp_state(rtp, RTGS_WAIT_GP);
+		rtp->gp_start = jiffies;
 		rtp->gp_func(rtp);
 
 		/* Invoke the callbacks. */
-- 
2.9.5