linux-kernel - [tip: locking/core] kernel/futex: Make futex_wait_requeue_pi() only call fixup

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Message-ID: <161548709514.398.3019777443206037709.tip-bot2@tip-bot2>
Date:   Thu, 11 Mar 2021 18:24:55 -0000
From:   "tip-bot2 for Davidlohr Bueso" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Davidlohr Bueso <dbueso@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/core] kernel/futex: Make futex_wait_requeue_pi() only
 call fixup_owner()

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     a1565aa4699847febfdfd6af3bf06ca17a9e16af
Gitweb:        https://git.kernel.org/tip/a1565aa4699847febfdfd6af3bf06ca17a9e16af
Author:        Davidlohr Bueso <dave@...olabs.net>
AuthorDate:    Fri, 26 Feb 2021 09:50:27 -08:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 11 Mar 2021 19:19:17 +01:00

kernel/futex: Make futex_wait_requeue_pi() only call fixup_owner()

A small cleanup that allows for fixup_pi_state_owner() only to be called
from fixup_owner(), and make requeue_pi uniformly call fixup_owner()
regardless of the state in which the fixup is actually needed. Of course
this makes the caller's first pi_state->owner != current check redundant,
but that should't really matter.

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20210226175029.50335-2-dave@stgolabs.net

---
 kernel/futex.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index db8002d..ee09995 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3241,15 +3241,14 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 	 * reference count.
 	 */
 
-	/* Check if the requeue code acquired the second futex for us. */
+	/*
+	 * Check if the requeue code acquired the second futex for us and do
+	 * any pertinent fixup.
+	 */
 	if (!q.rt_waiter) {
-		/*
-		 * Got the lock. We might not be the anticipated owner if we
-		 * did a lock-steal - fix up the PI-state in that case.
-		 */
 		if (q.pi_state && (q.pi_state->owner != current)) {
 			spin_lock(q.lock_ptr);
-			ret = fixup_pi_state_owner(uaddr2, &q, current);
+			ret = fixup_owner(uaddr2, &q, true);
 			/*
 			 * Drop the reference to the pi state which
 			 * the requeue_pi() code acquired for us.