From: Peter Oberparleiter Date: Tue, 26 Nov 2013 13:57:13 +0000 (+0100) Subject: s390/cio: Relax subchannel scan loop X-Git-Tag: v3.14-rc1~184^2~42 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b207f5a8f9a60fda4e995151af7d8670015e261d;p=pandora-kernel.git 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 Reviewed-by: Sebastian Ott Signed-off-by: Martin Schwidefsky --- Reading git-diff-tree failed