• Qian Cai's avatar
    mm/swap_state: mark various intentional data races · b96a3db2
    Qian Cai authored
    
    
    swap_cache_info.* could be accessed concurrently as noticed by
    KCSAN,
    
     BUG: KCSAN: data-race in lookup_swap_cache / lookup_swap_cache
    
     write to 0xffffffff85517318 of 8 bytes by task 94138 on cpu 101:
      lookup_swap_cache+0x12e/0x460
      lookup_swap_cache at mm/swap_state.c:322
      do_swap_page+0x112/0xeb0
      __handle_mm_fault+0xc7a/0xd00
      handle_mm_fault+0xfc/0x2f0
      do_page_fault+0x263/0x6f9
      page_fault+0x34/0x40
    
     read to 0xffffffff85517318 of 8 bytes by task 91655 on cpu 100:
      lookup_swap_cache+0x117/0x460
      lookup_swap_cache at mm/swap_state.c:322
      shmem_swapin_page+0xc7/0x9e0
      shmem_getpage_gfp+0x2ca/0x16c0
      shmem_fault+0xef/0x3c0
      __do_fault+0x9e/0x220
      do_fault+0x4a0/0x920
      __handle_mm_fault+0xc69/0xd00
      handle_mm_fault+0xfc/0x2f0
      do_page_fault+0x263/0x6f9
      page_fault+0x34/0x40
    
     Reported by Kernel Concurrency Sanitizer on:
     CPU: 100 PID: 91655 Comm: systemd-journal Tainted: G        W  O L 5.5.0-next-20200204+ #6
     Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
    
     write to 0xffffffff8d717308 of 8 bytes by task 11365 on cpu 87:
       __delete_from_swap_cache+0x681/0x8b0
       __delete_from_swap_cache at mm/swap_state.c:178
    
     read to 0xffffffff8d717308 of 8 bytes by task 11275 on cpu 53:
       __delete_from_swap_cache+0x66e/0x8b0
       __delete_from_swap_cache at mm/swap_state.c:178
    
    Both the read and write are done as lockless. Since swap_cache_info.*
    are only used to print out counter information, even if any of them
    missed a few incremental due to data races, it will be harmless, so just
    mark it as an intentional data race using the data_race() macro.
    
    While at it, fix a checkpatch.pl warning,
    
    WARNING: Single statement macros should not use a do {} while (0) loop
    
    Signed-off-by: default avatarQian Cai <cai@lca.pw>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Cc: Marco Elver <elver@google.com>
    Link: http://lkml.kernel.org/r/20200207003715.1578-1-cai@lca.pw
    
    
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    b96a3db2