[PATCH v3 0/2] cpu/hotplug: Fix cpuhp_cpu_state used before init

From: Steven Price <steven.price@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Vincent Donnefort <vincent.donnefort@arm.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Steven Price <steven.price@arm.com>,
	linux-kernel@vger.kernel.org, Baokun Li <libaokun1@huawei.com>,
	Dongli Zhang <dongli.zhang@oracle.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Yuan ZhaoXiong <yuanzhaoxiong@baidu.com>,
	YueHaibing <yuehaibing@huawei.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>
Subject: [PATCH v3 0/2] cpu/hotplug: Fix cpuhp_cpu_state used before init
Date: Mon, 11 Apr 2022 16:22:31 +0100	[thread overview]
Message-ID: <20220411152233.474129-1-steven.price@arm.com> (raw)

Currently it's possible to trigger a case where the cpuhp_cpu_state::cpu
member is used before it has been initialised. This can cause CPU 0 to
be erroneously marked as dying and trigger a scheduler panic (full
details in v1[1]).

The two patches here fix the root cause by removing the 'cpu' member
altogether and to prevent similar confusion in the future ensure that
the cpuhp_cpu_state structures are initialised before any hotplugging
occurs.

Changes since v2[2]:
 * Remove the cpu member altogether (first patch)
 * Move the initialisation of cpuhp_cpu_state as suggested by tglx
   (second patch)

[1] https://lore.kernel.org/all/20220225134918.105796-1-steven.price@arm.com/
[2] https://lore.kernel.org/all/20220316153637.288199-1-steven.price@arm.com/

Steven Price (2):
  cpu/hotplug: Remove the 'cpu' member of cpuhp_cpu_state
  cpu/hotplug: Initialise all cpuhp_cpu_state structs earlier

 kernel/cpu.c | 58 ++++++++++++++++++++++++++++------------------------
 1 file changed, 31 insertions(+), 27 deletions(-)

-- 
2.25.1