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bpf: Add bpf_cpumask_weight() kfunc

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It can be useful to query how many bits are set in a cpumask. For
example, if you want to perform special logic for the last remaining
core that's set in a mask. Let's therefore add a new
bpf_cpumask_weight() kfunc which checks how many bits are set in a mask.

Signed-off-by: David Vernet <void@manifault.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20231207210843.168466-2-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
David Vernet 2023-12-07 15:08:42 -06:00 committed by Alexei Starovoitov
parent 5181dc08f7
commit a6de18f310
2 changed files with 13 additions and 1 deletions
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2
Documentation/bpf/cpumasks.rst
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@ -352,7 +352,7 @@ can be used to query the contents of cpumasks.
.. kernel-doc:: kernel/bpf/cpumask.c
:identifiers: bpf_cpumask_first bpf_cpumask_first_zero bpf_cpumask_first_and
bpf_cpumask_test_cpu
bpf_cpumask_test_cpu bpf_cpumask_weight
.. kernel-doc:: kernel/bpf/cpumask.c
:identifiers: bpf_cpumask_equal bpf_cpumask_intersects bpf_cpumask_subset

12
kernel/bpf/cpumask.c
View File

@ -405,6 +405,17 @@ __bpf_kfunc u32 bpf_cpumask_any_and_distribute(const struct cpumask *src1,
return cpumask_any_and_distribute(src1, src2);
}
/**
* bpf_cpumask_weight() - Return the number of bits in @cpumask.
* @cpumask: The cpumask being queried.
*
* Count the number of set bits in the given cpumask.
*/
__bpf_kfunc u32 bpf_cpumask_weight(const struct cpumask *cpumask)
{
return cpumask_weight(cpumask);
}
__bpf_kfunc_end_defs();
BTF_SET8_START(cpumask_kfunc_btf_ids)
@ -432,6 +443,7 @@ BTF_ID_FLAGS(func, bpf_cpumask_full, KF_RCU)
BTF_ID_FLAGS(func, bpf_cpumask_copy, KF_RCU)
BTF_ID_FLAGS(func, bpf_cpumask_any_distribute, KF_RCU)
BTF_ID_FLAGS(func, bpf_cpumask_any_and_distribute, KF_RCU)
BTF_ID_FLAGS(func, bpf_cpumask_weight, KF_RCU)
BTF_SET8_END(cpumask_kfunc_btf_ids)
static const struct btf_kfunc_id_set cpumask_kfunc_set = {