Re: [PATCH v19 02/40] dept: add single event dependency tracker APIs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Critical] Unsafe macro conversion of functions causes double-evaluation of arguments, leading to logic bugs and memory corruption.
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commit e5795ffb367b1b68ef8574b0a67f0bf3654baf77
Author: Byungchul Park <byungchul@sk.com>

dept: add single event dependency tracker APIs

Wrapped the base APIs for easier annotation on wait and event. Start
with supporting waiters on each single event. More general support for
multiple events is a future work. Do more when the need arises.

> diff --git a/include/linux/dept_sdt.h b/include/linux/dept_sdt.h
> new file mode 100644
> index 0000000000000..0535f763b21be
> --- /dev/null
> +++ b/include/linux/dept_sdt.h
[ ... ]
> +#define sdt_map_init_key(m, k)		dept_map_init(m, k, 0, #m)
> +
> +#define sdt_wait(m)							\
> +	do {								\
> +		dept_request_event(m);					\
> +		dept_wait(m, 1UL, _THIS_IP_, __func__, 0);		\
> +	} while (0)

[Severity: Critical]
Can this macro evaluate its argument multiple times, causing a regression
if the argument contains side effects?

Unlike sdt_might_sleep_start(m) later in this file which safely captures
its argument in a local variable __m, sdt_wait(m) evaluates its argument
twice.

If an expression with a post-increment is passed to a macro like this,
the side effect will execute multiple times. This is especially risky
if existing synchronization primitives like wait_for_completion(x) are
converted into similar macros to integrate with the tracker.

For example, looking at drivers/vdpa/mlx5/core/resources.c:

mlx5_vdpa_add_res() {
	...
	while (completed < issued)
		wait_for_completion(&cmds[completed++].cmd_done);
	...
}

If wait_for_completion() or a similar wrapper evaluates its argument twice,
completed++ increments twice per loop iteration. This would skip completion
entries and eventually access out-of-bounds memory past the end of the cmds
array.

Could the argument be evaluated once and captured in a local variable
within these macros to avoid this?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260706061928.66713-1-byungchul@sk.com?part=2