scx_lavd: always inline submit_task_ctx to make the verifier happy #247
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In _some_ kernel versions, loading scx_lavd fails with an error of
"bpf_rcu_read_unlock is missing". The usage of
bpf_rcu_read_lock/unlock() in proc_dump_all_tasks() is correct but the
bpf verifier still think bpf_rcu_read_unlock() is missing. The most
plausible reason so far is that the problematic kernel does not have a
commit 6fceea0fa59f ("bpf: Transfer RCU lock state between subprog
calls"), failing inter-procedural analysis between proc_dump_all_tasks()
and submit_task_ctx(). Thus, we force inline submit_task_ctx() (no
inter-procedural analysis by the verifier is necessary) for the time
being.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Changwoo Min <changwoo@igalia.com>
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In some kernel versions, loading scx_lavd fails with an error of "bpf_rcu_read_unlock is missing". The usage of
bpf_rcu_read_lock/unlock() in proc_dump_all_tasks() is correct but the bpf verifier still think bpf_rcu_read_unlock() is missing. The most plausible reason so far is that the problematic kernel does not have a commit 6fceea0fa59f ("bpf: Transfer RCU lock state between subprog calls"), failing inter-procedural analysis between proc_dump_all_tasks() and
submit_task_ctx(). Thus, we force inline submit_task_ctx() (no inter-procedural analysis by the verifier is necessary) for the time being.
Suggested-by: Tejun Heo tj@kernel.org