linux-kernel - Re: [PATCH v2 07/19] lib/stackdepot: rework helpers for depot_alloc

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Message-ID: <CAG_fn=VspORKG5+xdkmnULq3C64mWCb-XGDvnV9htayf5CL-PQ@mail.gmail.com>
Date:   Mon, 9 Oct 2023 10:59:30 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     andrey.konovalov@...ux.dev
Cc:     Marco Elver <elver@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
        Evgenii Stepanov <eugenis@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH v2 07/19] lib/stackdepot: rework helpers for depot_alloc_stack

On Wed, Sep 13, 2023 at 7:15 PM <andrey.konovalov@...ux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@...gle.com>
>
> Split code in depot_alloc_stack and depot_init_pool into 3 functions:
>
> 1. depot_keep_next_pool that keeps preallocated memory for the next pool
>    if required.
>
> 2. depot_update_pools that moves on to the next pool if there's no space
>    left in the current pool, uses preallocated memory for the new current
>    pool if required, and calls depot_keep_next_pool otherwise.
>
> 3. depot_alloc_stack that calls depot_update_pools and then allocates
>    a stack record as before.
>
> This makes it somewhat easier to follow the logic of depot_alloc_stack
> and also serves as a preparation for implementing the eviction of stack
> records from the stack depot.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
Reviewed-by: Alexander Potapenko <glider@...gle.com>


> +static void depot_keep_next_pool(void **prealloc)
>  {
>         /*
> -        * If the next pool is already initialized or the maximum number of
> +        * If the next pool is already saved or the maximum number of
>          * pools is reached, do not use the preallocated memory.
>          */
>         if (!next_pool_required)
It's not mentioned at the top of the file that next_pool_required is
protected by pool_lock, but it is, correct?
Can you please update the comment to reflect that?


> +
> +       /*
> +        * At this point, either the next pool is kept or the maximum
> +        * number of pools is reached. In either case, take note that
> +        * keeping another pool is not required.
> +        * smp_store_release pairs with smp_load_acquire in stack_depot_save.

As I wrote in the other patch review, I think we'd better keep
parentheses at the end of the function names in the comments (unless
there's a style guide telling us not to).