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sched_ext: idle: Fix scx_bpf_pick_any_cpu_node() behavior

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When %SCX_PICK_IDLE_IN_NODE is specified, scx_bpf_pick_any_cpu_node()
should always return a CPU from the specified node, regardless of its
idle state.

Also clarify this logic in the function documentation.

Fixes: 01059219b0 ("sched_ext: idle: Introduce node-aware idle cpu kfunc helpers")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Andrea Righi 2025-02-25 10:37:42 +01:00 committed by Tejun Heo
parent 0e9b4c10e8
commit fde7d64766
1 changed files with 7 additions and 3 deletions
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10
kernel/sched/ext_idle.c
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@ -1029,8 +1029,9 @@ __bpf_kfunc s32 scx_bpf_pick_idle_cpu(const struct cpumask *cpus_allowed,
* empty.
*
* The search starts from @node and proceeds to other online NUMA nodes in
* order of increasing distance (unless SCX_PICK_IDLE_IN_NODE is specified,
* in which case the search is limited to the target @node).
* order of increasing distance (unless %SCX_PICK_IDLE_IN_NODE is specified,
* in which case the search is limited to the target @node, regardless of
* the CPU idle state).
*
* If ops.update_idle() is implemented and %SCX_OPS_KEEP_BUILTIN_IDLE is not
* set, this function can't tell which CPUs are idle and will always pick any
@ -1049,7 +1050,10 @@ __bpf_kfunc s32 scx_bpf_pick_any_cpu_node(const struct cpumask *cpus_allowed,
if (cpu >= 0)
return cpu;
cpu = cpumask_any_distribute(cpus_allowed);
if (flags & SCX_PICK_IDLE_IN_NODE)
cpu = cpumask_any_and_distribute(cpumask_of_node(node), cpus_allowed);
else
cpu = cpumask_any_distribute(cpus_allowed);
if (cpu < nr_cpu_ids)
return cpu;
else