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From: Byungchul Park <byungchul.park@lge.com>
To: peterz@infradead.org, mingo@kernel.org, rostedt@goodmis.org
Cc: tglx@linutronix.de, raistlin@linux.it,
	linux-kernel@vger.kernel.org, juri.lelli@gmail.com,
	bristot@redhat.com, kernel-team@lge.com
Subject: [RESEND PATCH v3 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value
Date: Mon,  8 Jan 2018 15:14:41 +0900	[thread overview]
Message-ID: <1515392081-32320-2-git-send-email-byungchul.park@lge.com> (raw)
In-Reply-To: <1515392081-32320-1-git-send-email-byungchul.park@lge.com>

Currently, migrating tasks to cpu0 unconditionally happens when the
heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
We have to distinguish between the empty case and cpu0 to avoid the
unnecessary migrations. Therefore, it has to return an invalid value
e.i. -1 in that case.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>
---
 kernel/sched/cpudeadline.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 9f02035..bcf903f 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 		int best_cpu = cpudl_maximum_cpu(cp);
 		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
 
+		/*
+		 * The heap tree is empty for now, just return.
+		 */
+		if (best_cpu == -1)
+			return 0;
+
 		if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
 		    dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
 			if (later_mask)
@@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
 		return -ENOMEM;
 	}
 
-	for_each_possible_cpu(i)
+	for_each_possible_cpu(i) {
+		cp->elements[i].cpu = -1;
 		cp->elements[i].idx = IDX_INVALID;
+	}
 
 	return 0;
 }
-- 
1.9.1

  reply	other threads:[~2018-01-08  6:15 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-08  6:14 [RESEND PATCH v3 1/2] sched/deadline: Add cpudl_maximum_dl() for clean-up Byungchul Park
2018-01-08  6:14 ` Byungchul Park [this message]
2018-06-01  6:12   ` [RESEND, v3, 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value Joel Fernandes
2018-06-01  6:18     ` Joel Fernandes
2018-06-01  7:10       ` Byungchul Park
2018-06-01 15:52         ` Joel Fernandes
2018-06-03  5:20           ` Byungchul Park
2018-01-11  9:07 ` [RESEND PATCH v3 1/2] sched/deadline: Add cpudl_maximum_dl() for clean-up Peter Zijlstra
2018-02-09  0:37   ` Byungchul Park
2018-02-26  7:51   ` Byungchul Park
2018-03-13  5:52   ` Byungchul Park
2018-04-23  7:01     ` Byungchul Park
2018-05-09  6:33   ` Byungchul Park
2018-05-25  5:13     ` Byungchul Park
2018-06-01  3:07       ` Byungchul Park
2018-06-01  6:02         ` Joel Fernandes
2018-06-01  6:30           ` Byungchul Park
  -- strict thread matches above, loose matches on Subject: below --
2017-12-28 23:32 Byungchul Park
2017-12-28 23:32 ` [RESEND PATCH v3 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value Byungchul Park
2017-12-19  1:19 [RESEND PATCH v3 1/2] sched/deadline: Add cpudl_maximum_dl() for clean-up Byungchul Park
2017-12-19  1:19 ` [RESEND PATCH v3 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value Byungchul Park

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