From: Wen Xiong <wenxiong@xxxxxxxxxxxxxxxxxx>
With b2a0eb1a0ac72869c910a79d935a0b049ec78ad9(nvme-pci: Remove watchdog
timer), EEH recovery stops working on ppc.
After removing whatdog timer routine, when trigger EEH on ppc, we hit
EEH in nvme_timeout(). We would like to check if pci channel is offline
or not at the beginning of nvme_timeout(), if it is already offline,
we don't need to do future nvme timeout process.
Add mrmory barrier before calling pci_channel_offline().
With the patch, EEH recovery works successfuly on ppc.
Signed-off-by: Wen Xiong <wenxiong@xxxxxxxxxxxxxxxxxx>