tree e69a7940ca8d51a6e1f639cf4df0b5e33925d357
parent 078f8ecaa30718694d1e13d9f415b7ce75b3c968
author Jan Glauber <jang@linux.vnet.ibm.com> 1294228069 +0100
committer Martin Schwidefsky <sky@mschwide.boeblingen.de.ibm.com> 1294228048 +0100

[S390] qdio: prevent race for shared indicators

If the shared indicator is used the following race leads to
an inbound stall:

Device                  CPU0                    CPU1
========================================================

non-shared DSCI =>1
ALSI => 1
                        Thin INT
                        ALSI => 0

                        non-shared DSCI
                        tasklets scheduled

shared DSCI => 1
ALSI => 1

                        shared DSCI => 0
                        ALSI ? -> set
                                                Thin INT
                                                ALSI => 0
                        ALSI was set,
                        shared DSCI => 1

After that no more interrupts occur because the DSCI is still set.
Fix that race by only resetting the shared DSCI if it was actually
set so the tasklets for all shared devices are scheduled and will
run after the interrupt.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>