linux-kernel - Re: [PATCH 1/2] wait: add wait_event_freezable_killable

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Message-ID: <fyx2kxtef3fha4timgtwrcwyacarb6g6tz66qjiehoi7ierslw@hkbdq5aguxnz>
Date: Mon, 9 Jun 2025 15:34:12 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Miklos Szeredi <miklos@...redi.hu>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, 
	Ben Segall <bsegall@...gle.com>, Tomasz Figa <tfiga@...omium.org>, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] wait: add wait_event_freezable_killable_exclusive

On (25/06/09 12:07), Sergey Senozhatsky wrote:
> Add a freezable variant of exclusive wait.  This can be useful
> in, for example, FUSE when system suspend occurs while FUSE is
> blocked on requests (which prevents system suspend.)
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> ---
>  include/linux/wait.h | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/include/linux/wait.h b/include/linux/wait.h
> index 327894f022cf..b98cfd094543 100644
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -657,6 +657,20 @@ do {										\
>  	__ret;									\
>  })
>  
> +#define __wait_event_freezable_killable_exclusive(wq, condition)		\
> +	___wait_event(wq, condition, (TASK_KILLABLE|TASK_FREEZABLE), 1, 0,	\
> +		      schedule())
> +
> +#define wait_event_freezable_killable_exclusive(wq, condition)			\
> +({										\
> +	int __ret = 0;								\
> +	might_sleep();								\
> +	if (!(condition))							\
> +		__ret = __wait_event_freezable_killable_exclusive(wq,		\
> +								  condition);	\
> +	__ret;									\
> +})

Or I can do something like:

+#define __wait_event_state_exclusive(wq, condition, state)			\
+	___wait_event(wq, condition, state, 1, 0, schedule())
+
+#define wait_event_state_exclusive(wq, condition, state)			\
+({										\
+	int __ret = 0;								\
+	might_sleep();								\
+	if (!(condition))							\
+		__ret = __wait_event_state_exclusive(wq, condition, state);	\
+	__ret;									\
+})


And then in fuse something like this:

@@ -207,8 +207,9 @@ static struct fuse_req *fuse_get_req(struct mnt_idmap *idmap,
 
 	if (fuse_block_alloc(fc, for_background)) {
 		err = -EINTR;
-		if (wait_event_killable_exclusive(fc->blocked_waitq,
-				!fuse_block_alloc(fc, for_background)))
+		if (wait_event_state_exclusive(fc->blocked_waitq,
+				!fuse_block_alloc(fc, for_background),
+				(TASK_KILLABLE|TASK_FREEZABLE)))
 			goto out;
 	}