linux-kernel - [PATCH v2 tip/core/rcu 08/18] rcu: Remove short-term CPU kicking

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Message-Id: <1484708037-2523-8-git-send-email-paulmck@linux.vnet.ibm.com>
Date:   Tue, 17 Jan 2017 18:53:47 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
        bobby.prani@...il.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH v2 tip/core/rcu 08/18] rcu: Remove short-term CPU kicking

Commit 4914950aaa12d ("rcu: Stop treating in-kernel CPU-bound workloads
as errors") added a (relatively) short-timeout call to resched_cpu().
This was inspired by as issue that was fixed by b7e7ade34e61 ("sched/core:
Fix remote wakeups").  But given that this issue was fixed, it is time
for the current commit to remove this call to resched_cpu().

Reported-by: Byungchul Park <byungchul.park@....com>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@...htriplett.org>
---
 kernel/rcu/tree.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0e61b62e3f4a..5a4aaad75e76 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1220,11 +1220,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
 		rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */
 	}
 
-	/* And if it has been a really long time, kick the CPU as well. */
-	if (ULONG_CMP_GE(jiffies,
-			 rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) ||
-	    ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs))
-		resched_cpu(rdp->cpu);  /* Force CPU into scheduler. */
 	/*
 	 * If more than halfway to RCU CPU stall-warning time, do
 	 * a resched_cpu() to try to loosen things up a bit.
-- 
2.5.2