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SubjectRe: [PATCH v6] workqueue: Fix edge cases for calc of pool's cpumask
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On 07/27/2017 01:15 PM, Michael Bringmann wrote:
>
> 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. Depending upon the order in which CPUs
> are added/removed, we may run into problems with the content of the
> cpumask used by the workqueues. This patch deals with situations where
> the online cpumask for a node is a proper superset of possible cpumask
> for the node. It also deals with edge cases where the order in which
> CPUs are removed/added from the online cpumask may leave the set for a
> node empty, and require execution by CPUs on another node.
>
> In these and other cases, the patch attempts to ensure that a valid,
> usable cpumask is used to set up newly created pools for workqueues.
> This patch provides a fix for NUMA systems which can add/subtract
> processors dynamically. The patch is expected to be an intermediate
> one while developers search for any underlying issues.
>
> [With additions to the patch provided by Tejun Hao <tj@kernel.org>]
>
> Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
> ---
> Changes in V6:
> -- Update descriptive text
> ---
> kernel/workqueue.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index c74bf39..6b6d540 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: onl intersect > "
^^^
This message doesn't seem right, or I am missing something, "onl"?

-Nathan

> + "possible intersect\n");
> + return false;
> + }
> +
> return !cpumask_equal(cpumask, attrs->cpumask);
>
> use_dfl:
>

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