linux-kernel - [PATCH] workqueue: Ensure that cpumask set for pools created after boot

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Date:   Wed, 10 May 2017 11:48:17 -0500
From:   Michael Bringmann <mwb@...ux.vnet.ibm.com>
To:     Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        Michael Bringmann <mwb@...ux.vnet.ibm.com>
Subject: [PATCH] workqueue: Ensure that cpumask set for pools created after
 boot

On NUMA systems with dynamic processors, the content of the cpumask
may change over time.  As new processors are added via DLPAR operations,
workqueues are created for them.  This patch ensures that the pools
created for new workqueues will be initialized with a cpumask before
the first worker is created, attached, and woken up.  If the mask is
not set up, then the kernel will crash when 'wakeup_process' is unable
to find a valid CPU to which to assign the new worker.

Signed-off-by: Michael Bringmann <mwb@...ux.vnet.ibm.com>
---
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c74bf39..6091069 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3366,6 +3366,8 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
 	copy_workqueue_attrs(pool->attrs, attrs);
 	pool->node = target_node;

+	cpumask_copy(pool->attrs->cpumask, cpumask_of(smp_processor_id()));
+
 	/*
 	 * no_numa isn't a worker_pool attribute, always clear it.  See
 	 * 'struct workqueue_attrs' comments for detail.