linux-kernel - [PATCH cgroup] https://github.com/raspberrypi/linux/issues/6631

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Message-ID: <20250201095145.32300-1-cynexium@proton.me>
Date: Sat,  1 Feb 2025 09:51:45 +0000
From: Umar Pathan <cynexium@...il.com>
To: tj@...nel.org
Cc: lizefan.x@...edance.com,
	hannes@...xchg.org,
	cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Umar Pathan <cynexium@...ton.me>
Subject: [PATCH cgroup] https://github.com/raspberrypi/linux/issues/6631

The existing freezer propagation logic improperly reduces
nr_frozen_descendants by an increasing 'desc' counter during unfreeze,
leading to:
- Premature parent cgroup unfreezing
- Negative descendant counts
- Broken hierarchy state consistency

Scenario demonstrating the bug:
1. Create hierarchy A->B->C
2. Freeze C (A/B freeze via propagation)
3. Freeze A->D (separate branch)
4. Unfreeze C -> A incorrectly unfreezes despite frozen D

Fixes: 711f763 ("freezer,cgroup: add freezer.stats subsystem")
Signed-off-by: Umar cynexium@...il.com
---
 kernel/cgroup/freezer.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c
index e9c15fbe5d9b..d384df2f53c2 100644
--- a/kernel/cgroup/freezer.c
+++ b/kernel/cgroup/freezer.c
@@ -304,6 +304,7 @@ void cgroup_freeze(struct cgroup *cgrp, bool freeze)
 			 */
 			if (dsct->freezer.e_freeze > 0)
 				continue;
+			
 			WARN_ON_ONCE(dsct->freezer.e_freeze < 0);
 		}
 
-- 
2.47.1