tree cf3888c460269cc7e29d43f78f952537ae3524d1
parent 6028f7c4cd87cac13481255d7e35dd2c9207ecae
author Benjamin Block <bblock@linux.ibm.com> 1572019968 +0200
committer Martin K. Petersen <martin.petersen@oracle.com> 1572315375 -0400

scsi: zfcp: implicitly refresh port-data diagnostics when reading sysfs

This patch adds implicit updates to the sysfs entries that read the
diagnostic data stored in the "caching buffer" for Exchange Port Data.

An update is triggered once the buffer is older than ZFCP_DIAG_MAX_AGE
milliseconds (5s). This entails sending an Exchange Port Data command to
the FCP-Channel, and during its ingress path updating the cached data and
the timestamp. To prevent multiple concurrent userspace-applications from
triggering this update in parallel we synchronize all of them using a
wait-queue (waiting threads are interruptible; the updating thread is not).

Link: https://lore.kernel.org/r/c145b5cfc99a63b6a018b1184fbd27bb09c955f5.1572018132.git.bblock@linux.ibm.com
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>