*.* !.gitignore !Makefile , 28 Nov 2016 18:41:45 -0600 Subject: scsi: cxlflash: Avoid command room violation During test, a command room violation interrupt is occasionally seen for the master context when the CXL flash devices are stressed. After studying the code, there could be gaps in the way command room value is being cached in cxlflash. When the cached command room is zero the thread attempting to send becomes burdened with updating the cached value with the actual value from the AFU. Today, this is handled with an atomic set operation of the raw value read. Following the atomic update, the thread proceeds to send. This behavior is incorrect on two counts: - The update fails to take into account the current thread and its consumption of one of the hardware commands. - The update does not take into account other threads also atomically updating. Per design, a worker thread updates the cached value when a send thread times out. By not protecting the update with a lock, the cached value can be incorrectly clobbered. To correct these issues, the update of the cached command room has been simplified and also protected using a spin lock which is held until the MMIO is complete. This ensures the command room is properly consumed by the same thread. Update of cached value also takes into account the current thread consuming a hardware command. Signed-off-by: Uma Krishnan Acked-by: Matthew R. Ochs Signed-off-by: Martin K. Petersen ---