SRU request for LP#235889

[Colin Ian King]

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/235889

SRU justification:

Impact: When starting up the Areca 1220 PCIe card webconfig tool the
system locks up with:

BUG: scheduling while atomic: archhttp64/7146/0x1000000001
BUG: soft lockup - CPU#0 stuck for 11s! [archhttp64:7146]
BUG: soft lockup - CPU#0 stuck for 11s! [archhttp64:7146]

Fix: Softlockup is caused by arcmsr_iop_message_xfer() being
called from atomic context under the queuecommand scsi_host_template
handler. The current GFP_KERNEL|GFP_DMA flags are wrong: firstly we are
in atomic context, secondly this memory is not used for DMA. The patch
attached corrects these issues.

Patch from upstream commit:
69e562c234440fb7410877b5b24f4b29ef8521d1

Testcase: Starting up Areca card with webconfig tool, system will lockup
without the patch.

Tested and verified OK by user from PPA kernel:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/235889/comments/22

Patch attached

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