ng the reasons why force_sig() is simply wrong here,
> force_sig(SIGTERM) looks strange. The task won't be killed if it has
> a handler, but SIG_IGN can't help. However if it has the handler
> but blocks SIGTERM temporary (this is very common) it will be killed.

Also,

> force_sig() can't kill the process if the main thread has already
> exited. IOW, it is trivial to create the process which can't be
> killed by sysrq.

So, this patch fixes the issue.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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