linux-kernel - Re: [PATCH 1/2 v4] cleanup: Add cond

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Date: Thu, 8 Feb 2024 14:04:03 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: "Fabio M. De Francesco" <fabio.maria.de.francesco@...ux.intel.com>
CC: Peter Zijlstra <peterz@...radead.org>, Dan Williams
	<dan.j.williams@...el.com>, <linux-kernel@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>, Dave Jiang
	<dave.jiang@...el.com>, Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH 1/2 v4] cleanup: Add cond_guard() to conditional guards

On Thu,  8 Feb 2024 14:04:23 +0100
"Fabio M. De Francesco" <fabio.maria.de.francesco@...ux.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@...wei.com>
I like the defensive else {}

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


> Cc: Peter Zijlstra <peterz@...radead.org>
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Suggested-by: Ira Weiny <ira.weiny@...el.com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@...ux.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)