coredump: abort core dump piping only due to a fatal signal

coredump: abort core dump piping only due to a fatal signal

Make wait_for_dump_helpers() not abort piping the core dump data when the
crashing process has received a non-fatal signal.  The abort still occurs
in the case of SIGKILL.

The rationale is that a crashing process may still receive uninteresting
signals such as SIGCHLD when its core dump data is being redirected to a
helper application.  While it's necessary to allow terminating the core
dump piping via SIGKILL, it's practically more useful for the purpose of
debugging and crash reporting if the core dump piping is not aborted due
to other non-fatal signals.

Signed-off-by: Ben Chan <benchan@chromium.org>
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>