linux-kernel - [tip: sched/urgent] sched/core: Fix a missed update of user_cpus

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Message-ID: <167645718309.4906.12679309805756202231.tip-bot2@tip-bot2>
Date:   Wed, 15 Feb 2023 10:33:03 -0000
From:   "tip-bot2 for Waiman Long" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Waiman Long <longman@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/urgent] sched/core: Fix a missed update of user_cpus_ptr

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     df14b7f9efcda35e59bb6f50351aac25c50f6e24
Gitweb:        https://git.kernel.org/tip/df14b7f9efcda35e59bb6f50351aac25c50f6e24
Author:        Waiman Long <longman@...hat.com>
AuthorDate:    Fri, 03 Feb 2023 13:18:49 -05:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 13 Feb 2023 16:36:14 +01:00

sched/core: Fix a missed update of user_cpus_ptr

Since commit 8f9ea86fdf99 ("sched: Always preserve the user requested
cpumask"), a successful call to sched_setaffinity() should always save
the user requested cpu affinity mask in a task's user_cpus_ptr. However,
when the given cpu mask is the same as the current one, user_cpus_ptr
is not updated. Fix this by saving the user mask in this case too.

Fixes: 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask")
Signed-off-by: Waiman Long <longman@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20230203181849.221943-1-longman@redhat.com
---
 kernel/sched/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e838feb..2a4918a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2951,8 +2951,11 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
 	}
 
 	if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
-		if (cpumask_equal(&p->cpus_mask, ctx->new_mask))
+		if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) {
+			if (ctx->flags & SCA_USER)
+				swap(p->user_cpus_ptr, ctx->user_mask);
 			goto out;
+		}
 
 		if (WARN_ON_ONCE(p == current &&
 				 is_migration_disabled(p) &&