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SubjectPossible race in mlx5_ib.ko

While searching for races in the Linux kernel I've come across
"drivers/infiniband/hw/mlx5/mlx5_ib.ko" module. Here are questions that
I came up with while analyzing results. Lines are given using the info
from Linux v4.12.

Consider the following case:

Thread 1: Thread 2:
->remove_keys limit_write
ent->cur--; if (ent->cur < ent->limit)
(mr.c: line 234) (mr.c: line 335)
err = add_keys(... ent->limit - ent->cur);

If size_write and limit_write are able to work concurrently with the
same ent then there is a possibility of a race between the accesses to
ent->cur. In worst case in limit_write new keys wouldn't be added. Is it
feasible from your point of view? If so, is it a benign race or a
serious one?

Thank you for your time.

-- Anton Volkov
Linux Verification Center, ISPRAS

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