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由 Roland Dreier 提交于
If ib_umem_release() is called after ib_uverbs_close() sets context->closing, then a process can get stuck in a D state, because the code boils down to if (down_write_trylock(&mm->mmap_sem)) down_write(&mm->mmap_sem); which is obviously a stupid instant deadlock. Fix the code so that we only try to take the lock once. This bug was introduced in commit f7c6a7b5 ("IB/uverbs: Export ib_umem_get()/ib_umem_release() to modules") which fortunately never made it into a release, and was reported by Pete Wyckoff <pw@osc.edu>. Signed-off-by: NRoland Dreier <rolandd@cisco.com>
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