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由 Robert Jennings 提交于
When an associativity level change is found for one thread, the siblings threads need to be updated as well. This is done today for PRRN in stage_topology_update() but is missing for VPHN in update_cpu_associativity_changes_mask(). This patch will correctly update all thread siblings during a topology change. Without this patch a topology update can result in a CPU in init_sched_groups_power() getting stuck indefinitely in a loop. This loop is built in build_sched_groups(). As a result of the thread moving to a node separate from its siblings the struct sched_group will have its next pointer set to point to itself rather than the sched_group struct of the next thread. This happens because we have a domain without the SD_OVERLAP flag, which is correct, and a topology that doesn't conform with reality (threads on the same core assigned to different numa nodes). When this list is traversed by init_sched_groups_power() it will reach the thread's sched_group structure and loop indefinitely; the cpu will be stuck at this point. The bug was exposed when VPHN was enabled in commit b7abef04 (v3.9). Cc: <stable@vger.kernel.org> [v3.9+] Reported-by: NJan Stancek <jstancek@redhat.com> Signed-off-by: NRobert Jennings <rcj@linux.vnet.ibm.com> Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
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