On Mon, 13 Feb 2017 19:00:42 -0200 "Guilherme G. Piccoli" <gpicc...@linux.vnet.ibm.com> wrote:
> Currently the xmon debugger is set only via kernel boot command-line. > It's disabled by default, and can be enabled with "xmon=on" on the > command-line. Also, xmon may be accessed via sysrq mechanism, but once > we enter xmon via sysrq, it's kept enabled until system is rebooted, > even if we exit the debugger. A kernel crash will then lead to xmon > instance, instead of triggering a kdump procedure (if configured), for > example. > > This patch introduces a debugfs entry for xmon, allowing user to query > its current state and change it if desired. Basically, the "xmon" file > to read from/write to is under the debugfs mount point, on powerpc > directory. Reading this file will provide the current state of the > debugger, one of the following: "on", "off", "early" or "nobt". Writing > one of these states to the file will take immediate effect on the debugger. > > Signed-off-by: Guilherme G. Piccoli <gpicc...@linux.vnet.ibm.com> > --- > * I had this patch partially done for some time, and after a discussion > at the kernel slack channel latest week, I decided to rebase and fix > some remaining bugs. I'd change 'x' option to always disable the debugger, > since with this patch we can always re-enable xmon, but today I noticed > Pan's patch on the mailing list, so perhaps his approach of adding a flag > to 'x' option is preferable. I can change this in a V2, if requested. > Thanks in advance! xmon state changing after the first sysrq+x violates principle of least astonishment, so I think that should be fixed. Then the question is, is it worth making it runtime configurable with xmon command or debugfs tunables? Thanks, Nick
