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authorPeter Oberparleiter <oberpar@linux.vnet.ibm.com>2013-11-26 14:57:13 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-12-16 14:37:40 +0100
commitb207f5a8f9a60fda4e995151af7d8670015e261d (patch)
treea74f52249f1f4ba9fce1f4d94a1bcaeef57ec991 /drivers/s390
parent449666dd1efacaf3f0eb020cc617dd702356575c (diff)
downloadop-kernel-dev-b207f5a8f9a60fda4e995151af7d8670015e261d.zip
op-kernel-dev-b207f5a8f9a60fda4e995151af7d8670015e261d.tar.gz
s390/cio: Relax subchannel scan loop
The CIO layer scans for newly available I/O devices by performing a scan of available subchannels using the Store Subchannel (STSCH) instruction. This processing can take a significant amount of time during which no other task can run on the same CPU (unless CONFIG_PREEMPT has been enabled). As a result, scheduling latencies for other tasks are increased noticeably, especially on a single-CPU system. Fix this problem by explicitly allowing other tasks to be scheduled each time a subchannel has been processed. Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com> Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'drivers/s390')
-rw-r--r--drivers/s390/cio/css.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 8c2cb87..c1f9cc7 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -553,6 +553,9 @@ static int slow_eval_unknown_fn(struct subchannel_id schid, void *data)
default:
rc = 0;
}
+ /* Allow scheduling here since the containing loop might
+ * take a while. */
+ cond_resched();
}
return rc;
}
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