linux-kernel - [patch V3 56/64] futex: Correct the number of requeued waiters for PI

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Message-ID: <20210805153956.051961951@linutronix.de>
Date:   Thu, 05 Aug 2021 17:13:56 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Davidlohr Bueso <dave@...olabs.net>,
        Mike Galbraith <efault@....de>
Subject: [patch V3 56/64] futex: Correct the number of requeued waiters for PI

From: Thomas Gleixner <tglx@...utronix.de>

The accounting is wrong when either the PI sanity check or the
requeue PI operation fails. Adjust it in the failure path.

Will be simplified in the next step.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/futex.c |    4 ++++
 1 file changed, 4 insertions(+)
---
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2131,6 +2131,8 @@ static int futex_requeue(u32 __user *uad
 
 		/* Ensure we requeue to the expected futex for requeue_pi. */
 		if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) {
+			/* Don't account for it */
+			task_count--;
 			ret = -EINVAL;
 			break;
 		}
@@ -2172,6 +2174,8 @@ static int futex_requeue(u32 __user *uad
 				 */
 				this->pi_state = NULL;
 				put_pi_state(pi_state);
+				/* Don't account for it */
+				task_count--;
 				/*
 				 * We stop queueing more waiters and let user
 				 * space deal with the mess.