Re: [PATCHv2 14/17] nvme: fix Clang context analysis warning in rdma.c

[Nilay Shroff]

> See patch below; to avoid more dependency issues for you, I suggest you
> pick it up and carry it as part of this series unless someone else wants
> it before for other reasons.
>
> Only lightly tested, please test.

Thanks! this is useful and it's working as expected. So, yes I will pick it
up and send out while I spin the next version of this series.

> ------ >8 ------
>
> From: Marco Elver <elver@xxxxxxxxxx>
> Date: Tue, 30 Jun 2026 12:01:26 +0200
> Subject: [PATCH] list: Permit context-unguarded access with
>   list_empty_careful()
>
> With Context Analysis (viz. Clang's Thread Safety Analysis), list_heads
> that are __guarded_by(..) require holding the appropriate context lock
> when accessing and manipulating them via the list API. Because Clang's
> warning diagnostics do not perform inter-procedural analysis, this is
> enforced by Clang with -Wthread-safety-pointer in the caller at the call
> boundary; a warning is produced when passing a pointer to a guarded
> variable without holding the appropriate context locks:
>
>    warning: passing pointer to variable 'list' requires holding [...] [-Wthread-safety-pointer]
>             if (list_empty(&ctrl->list))
>
> An exception is list_empty_careful(), which is like list_empty(), except
> that it is permitted to use without holding any context lock (carefully).
>
> Mark list_empty_careful() __context_unsafe, which disables context
> analysis within list_empty_careful(), but also suppresses warnings
> generated in callers related to its pointer arguments.
>
> Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
> ---
>   include/linux/list.h | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/list.h b/include/linux/list.h
> index 09d979976b3b..ba3c255f6112 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -436,6 +436,7 @@ static inline void list_del_init_careful(struct list_head *entry)
>    * if another CPU could re-list_add() it.
>    */
>   static inline int list_empty_careful(const struct list_head *head)
> +	__context_unsafe(/* intentional lockless access to @head */)
>   {
>   	struct list_head *next = smp_load_acquire(&head->next);
>   	return list_is_head(next, head) && (next == READ_ONCE(head->prev));

Thanks,
--Nilay