linux-kernel - Re: [RFC PATCH 1/6] task_work: Provide means to check if a work is queued

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Date: Tue, 25 Jun 2024 16:15:39 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Frederic Weisbecker <frederic@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 1/6] task_work: Provide means to check if a work is
 queued

On 06/25, Frederic Weisbecker wrote:
>
> --- a/kernel/task_work.c
> +++ b/kernel/task_work.c
> @@ -177,6 +177,7 @@ void task_work_run(void)
>
>  		do {
>  			next = work->next;
> +			work->next = TASK_WORK_DEQUEUED;

OK, but then the additional change below makes sense too?

Oleg.
---

--- x/kernel/task_work.c
+++ x/kernel/task_work.c
@@ -106,8 +106,10 @@ task_work_cancel_match(struct task_struc
 		if (!match(work, data)) {
 			pprev = &work->next;
 			work = READ_ONCE(*pprev);
-		} else if (try_cmpxchg(pprev, &work, work->next))
+		} else if (try_cmpxchg(pprev, &work, work->next)) {
+			work->next = TASK_WORK_DEQUEUED;
 			break;
+		}
 	}
 	raw_spin_unlock_irqrestore(&task->pi_lock, flags);