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authorHarald Freudenberger <freude@linux.ibm.com>2021-06-01 08:27:29 +0200
committerVasily Gorbik <gor@linux.ibm.com>2021-06-16 23:32:02 +0200
commite73a99f3287a740a07d6618e9470f4d6cb217da8 (patch)
tree3d25ace03dd51a422d33e4e614b795f0f86d5ce2 /arch
parent1874cb13d5d7cafa61ce93a760093ebc5485b6ab (diff)
s390/ap: Fix hanging ioctl caused by wrong msg counter
When a AP queue is switched to soft offline, all pending requests are purged out of the pending requests list and 'received' by the upper layer like zcrypt device drivers. This is also done for requests which are already enqueued into the firmware queue. A request in a firmware queue may eventually produce an response message, but there is no waiting process any more. However, the response was counted with the queue_counter and as this counter was reset to 0 with the offline switch, the pending response caused the queue_counter to get negative. The next request increased this counter to 0 (instead of 1) which caused the ap code to assume there is nothing to receive and so the response for this valid request was never tried to fetch from the firmware queue. This all caused a queue to not work properly after a switch offline/online and in the end processes to hang forever when trying to send a crypto request after an queue offline/online switch cicle. Fixed by a) making sure the counter does not drop below 0 and b) on a successful enqueue of a message has at least a value of 1. Additionally a warning is emitted, when a reply can't get assigned to a waiting process. This may be normal operation (process had timeout or has been killed) but may give a hint that something unexpected happened (like this odd behavior described above). Signed-off-by: Harald Freudenberger <freude@linux.ibm.com> Cc: stable@vger.kernel.org Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch')
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