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authorMichael Bringmann <mwb@linux.vnet.ibm.com>2017-07-27 16:27:14 -0500
committerTejun Heo <tj@kernel.org>2017-07-28 11:05:52 -0400
commit1ad0f0a7aa1bf3bd42dcd108a96713d255eacd9f (patch)
treeadad9ec5dd0a10141e3b30b57c2fa83264c77e18
parent0a94efb5acbb6980d7c9ab604372d93cd507e4d8 (diff)
workqueue: Work around edge cases for calc of pool's cpumask
There is an underlying assumption/trade-off in many layers of the Linux system that CPU <-> node mapping is static. This is despite the presence of features like NUMA and 'hotplug' that support the dynamic addition/ removal of fundamental system resources like CPUs and memory. PowerPC systems, however, do provide extensive features for the dynamic change of resources available to a system. Currently, there is little or no synchronization protection around the updating of the CPU <-> node mapping, and the export/update of this information for other layers / modules. In systems which can change this mapping during 'hotplug', like PowerPC, the information is changing underneath all layers that might reference it. This patch attempts to ensure that a valid, usable cpumask attribute is used by the workqueue infrastructure when setting up new resource pools. It prevents a crash that has been observed when an 'empty' cpumask is passed along to the worker/task scheduling code. It is intended as a temporary workaround until a more fundamental review and correction of the issue can be done. [With additions to the patch provided by Tejun Hao <tj@kernel.org>] Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--kernel/workqueue.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 7146ea70a62d..ca937b0c3a96 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3577,6 +3577,13 @@ static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
/* yeap, return possible CPUs in @node that @attrs wants */
cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
+
+ if (cpumask_empty(cpumask)) {
+ pr_warn_once("WARNING: workqueue cpumask: online intersect > "
+ "possible intersect\n");
+ return false;
+ }
+
return !cpumask_equal(cpumask, attrs->cpumask);
use_dfl: