* [BUG] fpga: dfl: possible ABBA deadlock in dfl_fpga_cdev_assign_port() and fme_pr()
@ 2021-11-23 7:55 Jia-Ju Bai
2021-11-24 15:59 ` Wu, Hao
0 siblings, 1 reply; 2+ messages in thread
From: Jia-Ju Bai @ 2021-11-23 7:55 UTC (permalink / raw)
To: hao.wu, trix, mdf; +Cc: linux-fpga, linux-kernel
Hello,
My static analysis tool reports a possible ABBA deadlock in the dfl
driver in Linux 5.10:
dfl_fpga_cdev_assign_port()
mutex_lock(&cdev->lock); --> Line 1067 (Lock A)
mutex_lock(&pdata->lock); --> Line 1624 (Lock B)
fme_pr()
mutex_lock(&pdata->lock); --> Line 126 (Lock B)
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
^ permalink raw reply [flat|nested] 2+ messages in thread
* RE: [BUG] fpga: dfl: possible ABBA deadlock in dfl_fpga_cdev_assign_port() and fme_pr()
2021-11-23 7:55 [BUG] fpga: dfl: possible ABBA deadlock in dfl_fpga_cdev_assign_port() and fme_pr() Jia-Ju Bai
@ 2021-11-24 15:59 ` Wu, Hao
0 siblings, 0 replies; 2+ messages in thread
From: Wu, Hao @ 2021-11-24 15:59 UTC (permalink / raw)
To: Jia-Ju Bai, trix@redhat.com, mdf@kernel.org
Cc: linux-fpga@vger.kernel.org, linux-kernel
>
> 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
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-11-23 7:55 [BUG] fpga: dfl: possible ABBA deadlock in dfl_fpga_cdev_assign_port() and fme_pr() Jia-Ju Bai
2021-11-24 15:59 ` Wu, Hao
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