linux-kernel - [PATCH V14 4/4] powerpc/vphn: Fix numa update end-loop bug

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Message-Id: <b6e0b987-8e45-77f1-c627-0df38979369a@linux.vnet.ibm.com>
Date:   Fri, 8 Sep 2017 15:47:56 -0500
From:   Michael Bringmann <mwb@...ux.vnet.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        John Allen <jallen@...ux.vnet.ibm.com>
Subject: [PATCH V14 4/4] powerpc/vphn: Fix numa update end-loop bug

powerpc/vphn: On Power systems with shared configurations of CPUs
and memory, there are some issues with the association of additional
CPUs and memory to nodes when hot-adding resources.  This patch
fixes an end-of-updates processing problem observed occasionally
in numa_update_cpu_topology().

Signed-off-by: Michael Bringmann <mwb@...ux.vnet.ibm.com>
---
Changes in V14:
  -- More code cleanup
---
 arch/powerpc/mm/numa.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 32f5f8d..ec098b3 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1401,16 +1401,22 @@ int numa_update_cpu_topology(bool cpus_locked)
 
 		for_each_cpu(sibling, cpu_sibling_mask(cpu)) {
 			ud = &updates[i++];
+			ud->next = &updates[i];
 			ud->cpu = sibling;
 			ud->new_nid = new_nid;
 			ud->old_nid = numa_cpu_lookup_table[sibling];
 			cpumask_set_cpu(sibling, &updated_cpus);
-			if (i < weight)
-				ud->next = &updates[i];
 		}
 		cpu = cpu_last_thread_sibling(cpu);
 	}
 
+	/*
+	 * Prevent processing of 'updates' from overflowing array
+	 * where last entry filled in a 'next' pointer.
+	 */
+	if (i)
+		updates[i-1].next = NULL;
+
 	pr_debug("Topology update for the following CPUs:\n");
 	if (cpumask_weight(&updated_cpus)) {
 		for (ud = &updates[0]; ud; ud = ud->next) {