linux-kernel - Re: [PATCH drivers/perf: hisi:] drivers/perf: hisi: fix NULL pointer issue when uninstall hns3 pmu driver

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Message-ID: <9579f762-24ce-0826-dc7b-2c79c969f192@huawei.com>
Date:   Wed, 11 Oct 2023 16:37:49 +0800
From:   Jijie Shao <shaojijie@...wei.com>
To:     Yicong Yang <yangyicong@...wei.com>, <will@...nel.org>,
        <jonathan.cameron@...wei.com>, <mark.rutland@....com>,
        <yangyicong@...ilicon.com>
CC:     <shaojijie@...wei.com>, <chenhao418@...wei.com>,
        <shenjian15@...wei.com>, <wangjie125@...wei.com>,
        <liuyonglong@...wei.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH drivers/perf: hisi:] drivers/perf: hisi: fix NULL pointer
 issue when uninstall hns3 pmu driver


on 2023/10/10 17:32, Yicong Yang wrote:
> Hi Jijie,
>
> On 2023/10/9 18:50, Jijie Shao wrote:
>> From: Hao Chen <chenhao418@...wei.com>
>>
>> When uninstall hns3 pmu driver, it will call cpuhp_state_remove_instance()
>> and then callback function hns3_pmu_offline_cpu() is called, it may cause
>> NULL pointer call trace when other driver is installing or uninstalling
>> concurrently.
>>
> More information about the calltrace you've met and how to reproduce this?
> I'm not sure why other drivers are involved.
>
>> As John Garry's opinion, cpuhp_state_remove_instance() is used for shared
>> interrupt, and using cpuhp_state_remove_instance_nocalls() is fine for PCIe
>> or HNS3 pmu.
>>
> I'm a bit confused here. We need to update the using CPU and migrate the perf
> context as well as the interrupt affinity in cpuhp::teardown() callback, so
> it make sense to not call this on driver detachment. But I cannot figure
> out why this is related to the shared interrupt, more details?
>
ok，I will send v2 to add more details.
Thanks