linux-kernel - [PATCH v3 0/2] cpu/hotplug: Fix cpuhp_cpu

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

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