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SubjectRe: [PATCH] ubi: Fix deadlock caused by recursively holding work_sem
----- Ursprüngliche Mail -----
> Von: "chengzhihao1" <chengzhihao1@huawei.com>
>> During the processing of the bgt, if the sync_erase() return -EBUSY
>> or some other error code in __erase_worker(),schedule_erase() called
>> again lead to the down_read(ubi->work_sem) hold twice and may get
>> block by down_write(ubi->work_sem) in ubi_update_fastmap(),
>> which cause deadlock.
>>
>> ubi bgt other task
>> do_work
>> down_read(&ubi->work_sem) ubi_update_fastmap
>> erase_worker # Blocked by down_read
>> __erase_worker down_write(&ubi->work_sem)
>> schedule_erase
>> schedule_ubi_work
>> down_read(&ubi->work_sem)
>>
>> Fix this by changing input parameter @nested of the schedule_erase() to
>> 'true' to avoid recursively acquiring the down_read(&ubi->work_sem).
>>
>> Also, fix the incorrect comment about @nested parameter of the
>> schedule_erase() because when down_write(ubi->work_sem) is held, the
>> @nested is also need be true.
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217093
>> Fixes: 2e8f08deabbc ("ubi: Fix races around ubi_refill_pools()")
>> Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>
>> ---
>> drivers/mtd/ubi/wl.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>

Applied to -next. Thanks everyone!

Thanks,
//richard

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