persistent_ram: check PERSISTENT_RAM_SIG before writing

if the PERSISTENT_RAM_SIG was corrupted, do not write something
to the persistent_ram buffer. this may cause the abnormal crash.

Change-Id: Ibd3082f7abeaa0e2e4b8f5022360977ec29add6f
block: add REQ_URGENT to request flags

This patch adds a new flag to be used in cmd_flags field of struct request
for marking request as urgent.
Urgent request is the one that should be given priority currently handled
(regular) request by the device driver. The decision of a request urgency
is taken by the scheduler.

Change-Id: Ic20470987ef23410f1d0324f96f00578f7df8717
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
msm: rpc: hold spinlock while doing wait_event

To prevent a race condition between wake_up called by
msm_rpcrouter_xprt_notify and wait_event in rr_read
hold a spinlock irqsave to prevent the system from going into
sleep when there is pending SMD data to process.

CRs-Fixed: 393416
Change-Id: Ic329c785fa8272857b7f067819d51a516a9cdc0d
Signed-off-by: Angshuman Sarkar <angshuman@codeaurora.org>
ARM: fault: assume no context when IRQs are disabled during data abort.

Bail out early if IRQs are disabled in do_page_fault or else
  [14415.157266] BUG: sleeping function called from invalid context at arch/arm/mm/fault.c:301

Russell King's idea from
  http://comments.gmane.org/gmane.linux.ports.arm.omap/59256

Signed-off-by: JP Abgrall <jpa@google.com>