sched/cache: Fix has_multi_llcs iff at least one partition has multiple LLCs

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sched_cache_present is a global static key, but build_sched_domains()
is called per partition from the "Build new domains" loop in
partition_sched_domains_locked(). Each call unconditionally sets the
key based solely on the has_multi_llcs local variable for that partition.

The call to the last partition set the value even when there
are previous partitions with multiple LLCs.

If partition A (multi-LLC) is built first, the key is enabled. Then
when partition B (single-LLC) is built, the key is disabled. The
multi-LLC partition A is still active but the key is now off.

Fix it by doing a similar thing as sched_energy_present: check the
multi-LLCs during the iteration over all the partitions rather than
checking it on a single partition.

This bug was reported by sashiko.

Fixes: d59f4fd1d3 ("sched/cache: Enable cache aware scheduling for multi LLCs NUMA node")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/c541af2547d54509fbfd3b3a1e8072e2e5c7ff68.1778703694.git.tim.c.chen@linux.intel.com

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Chen Yu 2026-05-13 13:39:25 -07:00 • committed by Peter Zijlstra

parent 5beff4f087

commit a7660ce159

1 changed files with 53 additions and 16 deletions

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kernel/sched/topology.c

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