From: tip-bot for Tejun Heo <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: htejun@gmail.com, ego@linux.vnet.ibm.com, peterz@infradead.org,
tglx@linutronix.de, tj@kernel.org, torvalds@linux-foundation.org,
mpe@ellerman.id.au, linux-kernel@vger.kernel.org,
aneesh.kumar@linux.vnet.ibm.com, abdhalee@linux.vnet.ibm.com,
mingo@kernel.org, hpa@zytor.com
Subject: [tip:sched/urgent] sched/core: Allow kthreads to fall back to online && !active cpus
Date: Fri, 24 Jun 2016 02:00:32 -0700 [thread overview]
Message-ID: <tip-feb245e304f343cf5e4f9123db36354144dce8a4@git.kernel.org> (raw)
In-Reply-To: <20160616193504.GB3262@mtj.duckdns.org>
Commit-ID: feb245e304f343cf5e4f9123db36354144dce8a4
Gitweb: http://git.kernel.org/tip/feb245e304f343cf5e4f9123db36354144dce8a4
Author: Tejun Heo <htejun@gmail.com>
AuthorDate: Thu, 16 Jun 2016 15:35:04 -0400
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 24 Jun 2016 08:26:53 +0200
sched/core: Allow kthreads to fall back to online && !active cpus
During CPU hotplug, CPU_ONLINE callbacks are run while the CPU is
online but not active. A CPU_ONLINE callback may create or bind a
kthread so that its cpus_allowed mask only allows the CPU which is
being brought online. The kthread may start executing before the CPU
is made active and can end up in select_fallback_rq().
In such cases, the expected behavior is selecting the CPU which is
coming online; however, because select_fallback_rq() only chooses from
active CPUs, it determines that the task doesn't have any viable CPU
in its allowed mask and ends up overriding it to cpu_possible_mask.
CPU_ONLINE callbacks should be able to put kthreads on the CPU which
is coming online. Update select_fallback_rq() so that it follows
cpu_online() rather than cpu_active() for kthreads.
Reported-by: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@fb.com
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20160616193504.GB3262@mtj.duckdns.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4135ac8..51d7105 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1536,7 +1536,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
for (;;) {
/* Any allowed, online CPU? */
for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
- if (!cpu_active(dest_cpu))
+ if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu))
+ continue;
+ if (!cpu_online(dest_cpu))
continue;
goto out;
}
next prev parent reply other threads:[~2016-06-24 9:01 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <573D9C2D.4020609@linux.vnet.ibm.com>
[not found] ` <20160526151137.GA26508@in.ibm.com>
2016-06-07 12:29 ` WARNING at kernel/sched/core.c:1166 while booting 4.6.0 mainline on ppc64le bare metal Abdul Haleem
2016-06-07 15:14 ` [PATCH 0/2] Fix CPU Online handling for unbounded worker threads Gautham R. Shenoy
2016-06-07 15:14 ` [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the beginning of CPU_ONLINE Gautham R. Shenoy
2016-06-15 15:53 ` Tejun Heo
2016-06-15 19:28 ` Gautham R Shenoy
2016-06-16 19:35 ` Tejun Heo
2016-06-21 14:12 ` Gautham R Shenoy
2016-06-21 15:36 ` Tejun Heo
2016-06-21 19:37 ` Peter Zijlstra
2016-06-21 19:43 ` Tejun Heo
2016-06-21 19:47 ` Peter Zijlstra
2016-06-22 5:15 ` Gautham R Shenoy
2016-06-24 9:00 ` tip-bot for Tejun Heo [this message]
2016-06-07 15:14 ` [PATCH 2/2] workqueue:Fix affinity of an unbound worker of a node with 1 online CPU Gautham R. Shenoy
2016-06-08 6:03 ` Abdul Haleem
2016-06-14 11:22 ` Peter Zijlstra
2016-06-15 10:19 ` Gautham R Shenoy
2016-06-15 11:32 ` Peter Zijlstra
2016-06-15 12:50 ` Gautham R Shenoy
2016-06-15 13:14 ` Peter Zijlstra
2016-06-15 16:01 ` Tejun Heo
2016-06-16 12:11 ` Michael Ellerman
2016-06-16 12:45 ` Peter Zijlstra
2016-06-16 19:39 ` Tejun Heo
2016-06-17 1:49 ` Michael Ellerman
2016-07-15 5:27 ` Gautham R Shenoy
[not found] ` <57887507.911f240a.687de.08c5SMTPIN_ADDED_BROKEN@mx.google.com>
2016-07-15 12:10 ` Tejun Heo
2016-06-13 5:44 ` [PATCH 0/2] Fix CPU Online handling for unbounded worker threads Gautham R Shenoy
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