• Michal Hocko's avatar
    mm, oom_reaper: do not mmput synchronously from the oom reaper context · ec8d7c14
    Michal Hocko authored
    Tetsuo has properly noted that mmput slow path might get blocked waiting
    for another party (e.g.  exit_aio waits for an IO).  If that happens the
    oom_reaper would be put out of the way and will not be able to process
    next oom victim.  We should strive for making this context as reliable
    and independent on other subsystems as much as possible.
    
    Introduce mmput_async which will perform the slow path from an async
    (WQ) context.  This will delay the operation but that shouldn't be a
    problem because the oom_reaper has reclaimed the victim's address space
    for most cases as much as possible and the remaining context shouldn't
    bind too much memory anymore.  The only exception is when mmap_sem
    trylock has failed which shouldn't happen too often.
    
    The issue is only theoretical but not impossible.
    Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
    Reported-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
    Cc: David Rientjes <rientjes@google.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    ec8d7c14
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