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List: linux-fpga
Subject: RE: [BUG] fpga: dfl: possible ABBA deadlock in dfl_fpga_cdev_assign_port() and fme_pr()
From: "Wu, Hao" <hao.wu () intel ! com>
Date: 2021-11-24 15:59:57
Message-ID: DM6PR11MB38195CE729A5765E019C226285619 () DM6PR11MB3819 ! namprd11 ! prod ! outlook ! com
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>
> dfl_fpga_cdev_assign_port()
> mutex_lock(&cdev->lock); --> Line 1067 (Lock A)
> mutex_lock(&pdata->lock); --> Line 1624 (Lock B)
This lock is from port platform device.
>
> fme_pr()
> mutex_lock(&pdata->lock); --> Line 126 (Lock B)
This lock is from fme platform device.
Actually they are different locks, but yes, maybe we should consider
improving the naming to avoid misunderstanding.
Thanks
Hao
> fpga_region_program_fpga()
> fpga_bridges_enable()
> fpga_bridge_enable()
> fme_bridge_enable_set() --> function pointer via
> "bridge->br_ops->enable_set()"
> dfl_fpga_cdev_find_port()
> mutex_lock(&cdev->lock); --> Line 499 (LockA)
>
> When dfl_fpga_cdev_assign_port() and fme_pr() are concurrently executed,
> the deadlock can occur.
>
> I am not quite sure whether this possible deadlock is real and how to
> fix it if it is real.
> Any feedback would be appreciated, thanks
>
> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
>
>
> Best wishes,
> Jia-Ju Bai
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