Re: [PATCH v1 4/5] perf bpf-filter: Extend lock_held() to support RCU, Tasks Trace RCU, and SRCU

[sashiko-bot@kernel.org]

> Extend the lock_held(<lock>) BPF sample filter to support RCU, Tasks
> Trace RCU, and SRCU locks:
> 
> - 'rcu' (supports both read/shared and write/exclusive modes):
>   - Read/shared ('lock_held_read(rcu)', 'lock_held(rcu:R)',
>     'lock_held(rcu_read_lock)'): directly inspects
>     current->rcu_read_lock_nesting in perf_sample_filter via CO-RE (on
>     CONFIG_PREEMPT_RCU kernels), accounting for the baseline
>     rcu_read_lock() nesting acquired by the perf overflow handler itself
>     (bpf_overflow_handler() and do_perf_sw_event()) with zero extra
>     fentry/fexit tracing hooks.
>   - Write/exclusive ('lock_held_write(rcu)', 'lock_held(rcu:W)'):
>     attaches fentry/fexit hooks to synchronize_rcu(),
>     synchronize_rcu_expedited(), synchronize_rcu_tasks(), and
>     rcu_barrier() to track grace-period and barrier waits.
> [ ... ]
> 
>   # perf record -a -g -e task-clock --filter 'lock_held(rcu:W)' -- sleep 1
>   # perf record -a -g -e cycles --filter 'lock_held(srcu)' -- sleep 1
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261017054555.1655407-1-irogers@google.com?part=4