Re: [PATCH v3] Drivers: hv: Avoid infinite retry loop in init_vp_index()
From: sashiko-bot@kernel.org
Date: 2026-08-27 19:56:29
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: Pre-existing issues: - [High] This problem wasn't introduced by this patch, but the patch attempts to fix an infinite retry loop while relying on a flawed assumption, leaving a kernel hang scenario intact under CPU hotplug. -- commit 357edd9f97074f4d93f3160be466a7aa7d20c7bb Author: Waiman Long [off-list ref] Drivers: hv: Avoid infinite retry loop in init_vp_index() This commit attempts to fix an infinite retry loop in init_vp_index() by skipping NUMA nodes that do not contain any housekeeping CPUs. It aims to ensure that a NUMA node with housekeeping CPUs is eventually found. Link: https://sashiko.dev/#/message/20260422030903.E1BFCC2BCB0%40smtp.kernel.org [1]
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diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index a044fd3b3c4e7..2e611d2de6d10 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c
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@@ -780,14 +781,16 @@ static void init_vp_index(struct vmbus_channel *channel) next_numa_node_id = 0; continue; } - if (cpumask_empty(cpumask_of_node(numa_node))) + node_mask = cpumask_of_node(numa_node); + if (cpumask_empty(node_mask) || + !cpumask_intersects(node_mask, hk_mask)) continue; break; }
[Severity: High] This is a pre-existing issue, but the patch attempts to fix an infinite retry loop while relying on an assumption that leaves a kernel hang scenario intact under CPU hotplug. Could this while (true) loop in init_vp_index() iterate endlessly without sleeping if an administrator dynamically hot-offlines all managed IRQ housekeeping CPUs? Since housekeeping_cpumask(HK_TYPE_MANAGED_IRQ) tracks all possible housekeeping CPUs, the early abort check at the start of the function will see hk_mask as non-empty even if those CPUs are currently offline. However, cpumask_of_node() only returns online CPUs. If the remaining managed IRQ housekeeping CPUs are offlined, cpumask_intersects(node_mask, hk_mask) will evaluate to false for every NUMA node, causing this loop to spin indefinitely while holding channel_mutex and cpus_read_lock(). -- Sashiko AI review · https://sashiko.dev/#/patchset/20260827193750.662623-1-longman@redhat.com?part=1