Re: [PATCH 1/2 v4] cleanup: Add cond_guard() to conditional guards

Jonathan Cameron
2024-02-08T14:04:08Z

On Thu, 8 Feb 2024 14:04:23 +0100
"Fabio M. De Francesco" <fabio.maria.de.francesco@linux.intel.com> wrote:

> Add cond_guard() macro to conditional guards.
>
> cond_guard() is a guard to be used with the conditional variants of locks,
> like down_read_trylock() or mutex_lock_interruptible().
>
> It takes a statement (or statement-expression) that is passed as its
> second argument. That statement (or statement-expression) is executed if
> waiting for a lock is interrupted or if a _trylock() fails in case of
> contention.
>
> Usage example:
>
> cond_guard(mutex_intr, return -EINTR, &mutex);
>
> Consistent with other usage of _guard(), locks are unlocked at the exit of the
> scope where cond_guard() is called.
>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
I like the defensive else {}

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
> ---
> include/linux/cleanup.h | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
> index c2d09bc4f976..7b54ee996414 100644
> --- a/include/linux/cleanup.h
> +++ b/include/linux/cleanup.h
> @@ -134,6 +134,16 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
> * an anonymous instance of the (guard) class, not recommended for
> * conditional locks.
> *
> + * cond_guard(name, fail, args...):
> + * a guard to be used with the conditional variants of locks, like
> + * down_read_trylock() or mutex_lock_interruptible. 'fail' is a
> + * statement or statement-expression that is executed if waiting for a
> + * lock is interrupted or if a _trylock() fails in case of contention.
> + *
> + * Example:
> + *
> + * cond_guard(mutex_intr, return -EINTR, &mutex);
> + *
> * scoped_guard (name, args...) { }:
> * similar to CLASS(name, scope)(args), except the variable (with the
> * explicit name 'scope') is declard in a for-loop such that its scope is
> @@ -165,6 +175,11 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
>
> #define __guard_ptr(_name) class_##_name##_lock_ptr
>
> +#define cond_guard(_name, _fail, args...) \
> + CLASS(_name, scope)(args); \
> + if (!__guard_ptr(_name)(&scope)) _fail; \
> + else { }
> +
> #define scoped_guard(_name, args...) \
> for (CLASS(_name, scope)(args), \
> *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)