• Oleg Nesterov's avatar
    dlm: kill the unnecessary and wrong device_close()->recalc_sigpending() · 201d3dfa
    Oleg Nesterov authored
    device_close()->recalc_sigpending() is not needed, sigprocmask() takes
    care of TIF_SIGPENDING correctly.
    
    And without ->siglock it is racy and wrong, it can wrongly clear
    TIF_SIGPENDING and miss a signal.
    
    But even with this patch device_close() is still buggy:
    
      1. sigprocmask() should not be used, we have set_task_blocked(),
         but this is minor.
    
      2. We should never block SIGKILL or SIGSTOP, and this is what
         the code tries to do.
    
      3. This can't protect against SIGKILL or SIGSTOP anyway. Another
         thread can do signal_wake_up(), say, do_signal_stop() or
         complete_signal() or debugger.
    
      4. sigprocmask(SIG_BLOCK, allsigs) doesn't necessarily clears
         TIF_SIGPENDING, say, freezing() or ->jobctl.
    
      5. device_write() looks equally wrong by the same reason.
    
    Looks like, this tries to protect some wait_event_interruptible() logic
    from signals, it should be turned into uninterruptible wait.  Or we need
    to implement something like signals_stop/start for such a use-case.
    Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    201d3dfa
user.c 24.5 KB