The following is a rewrite of the printk log levels (plus the added
print rate limit) as for Keir's suggestions.
This touches a lot so please test.
We have now four log levels to choose from, as well as a GUEST flag for
prints that are controlled by something that a guest does. I tried to
go though practically all DPRINTKs to see what level it should be and
whether or not a GUEST should be tagged to it. But, being human and not
knowing the fine details of the code surrounding the prints, I'm sure I
tagged things wrong. So that said, here are the new tags:
XENLOG_ERR - non guest fatal error message. The ship is sinking.
XENLOG_WARNING - non guest warning message, we can plug the holes.
XENLOG_INFO - non guest info message, counting the fish we catch.
XENLOG_DEBUG - non guest debug message, keep all fish, even if they are
under the limit.
XENLOG_G_ERR - guest fatal error, One of the boats is sinking.
XENLOG_G_WARNING - guest warning message, we can dump the water out.
XENLOG_G_INFO - guest info message, count the people on board.
XENLOG_G_DEBUG - guest debug message, smuggle the illegal immigrants.
Basically, we don't trust guests. So we differentiate the guest messages
with the _G_ option so that we can process these prints differently.
Basically, we add a print rate limit to them.
On a domain crash, I also added a oops_in_progress to notify that all
prints should be printed regardless.
There's also a xen_startup variable, that currently isn't set, but it
should be set to 1 on startup (print everything) and cleared after dom0
is up and running. I haven't added this in yet.
There's 4 thresholds too.
XENLOG_UPPER_THRESHOLD
XENLOG_LOWER_THRESHOLD
XENLOG_GUEST_UPPER_THRESHOLD
XENLOG_GUEST_LOWER_THRESHOLD
For both the non-guest and guest, they have an upper and lower
threshold. Since ERR is 0 and DEBUG is 3, what these thresholds
represent is that anything above the upper is ignored, anything below
the lower is always printed, and any thing in between (inclusive) is
rate limited.
If the lower is greater than the upper, then only the upper is
recognized, and there is no rate limiting performed. All above the
upper is ignored, and all below or equal to the upper is printed.
ToDo:
1) Have xen_startup = 1 on startup and turned to zero later.
2) Add a config option for changing the default thresholds
3) Having a keyhandler to change the default thresholds
4) Add a hypercall to let Dom0 change the default thresholds
5) Add a sysctl to have userspace in Dom0 change the default thresholds
(** seeing a pattern here? **)
6) Tag the bare printks to use the log levels.
Currently (as Keir suggested) the default thresholds are:
non guest: upper=1 lower=2 (ERR/WARNING printed, but nothing else)
guest: upper=1 lower=0 (ERR/WARNING print rated, nothing else printed)
Feel free to comment.
-- Steve
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