Re: [RFC PATCH 2/5] perf/core: add AUX ring accessors for kernel consumers

[sashiko-bot@kernel.org]

> From: Kunwu Chan <kunwu.chan@gmail.com>
> 
> Add kernel-consumer accessors for the published AUX producer head, the
> consumer tail, and copying a possibly wrapped AUX interval without exposing
> perf's internal page array.
> 
> Use the same memory ordering as mmap consumers: order data reads after the
> published head with smp_rmb() and order completed data reads before
> advancing the tail with smp_mb().  Validate cursor distances in the
> absolute cursor domain before applying the ring mask, so rewound,
> already-consumed, and future windows are rejected even across unsigned
> cursor wrap.
> 
> Hold an AUX reference while copying so storage cannot disappear under the
> consumer.  Restrict the helpers to buffers owned by the kernel AUX setup
> API.  Document the API in
> Documentation/userspace-api/perf_ring_buffer.rst (§3.4).
> 
> Co-developed-by: Lian Wang (Processmission) <lianux.mm@gmail.com>
> Signed-off-by: Lian Wang (Processmission) <lianux.mm@gmail.com>
> Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260814144927.489172-1-kunwu.chan@linux.dev?part=2