tree df5d69d40dbdaf5e5014a6ce41909e7236a196c1
parent 95b866d5afcafee00fc9ad70665e48c86d8c4e0f
author Heiko Carstens <heiko.carstens@de.ibm.com> 1223063699 +0200
committer Martin Schwidefsky <schwidefsky@de.ibm.com> 1223063754 +0200

[S390] nohz: Fix __udelay.

This fixes a regression that came with 934b2857cc576ae53c92a66e63fce7ddcfa74691
("[S390] nohz/sclp: disable timer on synchronous waits.").
If udelay() gets called from a disabled context it sets the clock comparator
to a value where it expects the next interrupt. When the interrupt happens
the clock comparator gets not reset and therefore the interrupt condition
doesn't get cleared. The result is an endless timer interrupt loop.

In addition this patch fixes also the following:

rcutorture reveals that our __udelay implementation is still buggy,
since it might schedule tasklets, but prevents their execution:

NOHZ: local_softirq_pending 42
NOHZ: local_softirq_pending 02
NOHZ: local_softirq_pending 142
NOHZ: local_softirq_pending 02

To fix this we make sure that only the clock comparator interrupt
is enabled when the enabled wait psw is loaded.
Also no code gets called anymore which might schedule tasklets.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>