Messages in this thread | | | Date | Thu, 14 Jan 2021 12:33:10 +0900 | From | Sergey Senozhatsky <> | Subject | madvise(MADV_REMOVE) deadlocks on shmem THP |
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Hi,
We are running into lockups during the memory pressure tests on our boards, which essentially NMI panic them. In short the test case is
- THP shmem echo advise > /sys/kernel/mm/transparent_hugepage/shmem_enabled
- And a user-space process doing madvise(MADV_HUGEPAGE) on new mappings, and madvise(MADV_REMOVE) when it wants to remove the page range
The problem boils down to the reverse locking chain: kswapd does
lock_page(page) -> down_read(page->mapping->i_mmap_rwsem)
madvise() process does
down_write(page->mapping->i_mmap_rwsem) -> lock_page(page)
CPU0 CPU1
kswapd vfs_fallocate() shrink_node() shmem_fallocate() shrink_active_list() unmap_mapping_range() page_referenced() << lock page:PG_locked >> unmap_mapping_pages() << down_write(mapping->i_mmap_rwsem) >> rmap_walk_file() zap_page_range_single() down_read(mapping->i_mmap_rwsem) << W-locked on CPU1>> unmap_page_range() rwsem_down_read_failed() __split_huge_pmd() __rwsem_down_read_failed_common() __lock_page() << PG_locked on CPU0 >> schedule() wait_on_page_bit_common() io_schedule()
-ss
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