[RFC] printk's sync mode for ftrace_dump()

[Sebastian Andrzej Siewior]

ftrace_dump() is used for instance by alt-sysrq-z / sysrq_ftrace_dump().
The function itself dumps the whole trace buffer in an irq-off section so
no need to talk about max latencies unless this is going to change.

The output on the serial is more or less brief and starts with
    "** 397774 printk messages dropped **"
and so I do see only the end of it. Might be okay.
Any reason not to use the sync mode + atomic console while ftrace_dump()
is in progress?

Sebastian