Re: [RFC PATCH v2 0/3] trace: stack trace deduplication for ftrace ring buffer

[Li Pengfei]

Hi Masami,

I went through the Sashiko comments on v2 [1]. Per-finding response
below; v3 will incorporate the fixes.

[1] https://sashiko.dev/#/patchset/20260522104017.1668638-1-lipengfei28%40xiaomi.com

Patch 1/3:

  - memset() torn reads against lockless readers: agreed, the
    reset path is not well serialized against tracefs readers.
    Will tighten slow-path synchronization in v3.

  - seq_next() not advancing *pos on EOF: agreed, will fix in v3.

  - atomic_read(&resetting) without acquire: agreed, will switch
    to atomic_read_acquire() in v3.

  - Plain reads of entry->key: agreed, will use READ_ONCE() in v3.

  - atomic64_inc() in NMI-safe hot path on 32-bit GENERIC_ATOMIC64:
    agreed, will move the counters off the hot path (local_t /
    per-CPU) in v3.

Patch 2/3:

  - TRACE_STACK_ID not in trace_valid_entry(): agreed, will add in v3.

  - "NULL from kzalloc" comment: wording bug, will correct in v3.

  - Reset memset synchronization: same fix as patch 1, finding 1.

Patch 3/3:

  - Selftest missing 'function:tracer' in '# requires:': agreed,
    will add in v3.

  - Selftest wiping the ring buffer via 'echo nop > current_tracer'
    before reading trace: agreed, will reorder in v3.

I'll send v3 once the changes are tested.

Pengfei