> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index f02254a21585..9923703a1544 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
[ ... ]
> +/*
> + * We keep 32 trampoline locks (5 bits) in the pool, because there
> + * is 48 (MAX_LOCK_DEPTH) locks limit allowed to be simultaneously
> + * held by task.
> + */
> +#define TRAMPOLINE_LOCKS_BITS 5
> +#define TRAMPOLINE_LOCKS_TABLE_SIZE (1 << TRAMPOLINE_LOCKS_BITS)
> +
> +static struct {
> + struct mutex mutex;
> + struct lock_class_key key;
> +} trampoline_locks[TRAMPOLINE_LOCKS_TABLE_SIZE];
During v1 review, Alexei asked to add a comment explaining both the
pool size of 32 and why per-lock class keys are needed:
https://lore.kernel.org/bpf/caadnvql_jpe_7a55htn5cyyoxwchahik3+cdeoeurqzauf+...@mail.gmail.com/
The comment explains the 32 count (MAX_LOCK_DEPTH limit), but does
it also need to mention why each lock has its own lock_class_key?
Without that, it is not obvious that distinct keys are required to
avoid lockdep "recursive locking" warnings when
trampoline_lock_all() acquires all 32 pool mutexes simultaneously.
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/23133791558
