Re: [PATCH v2] Add hard/soft lockup debugger entry points

From: Chris Metcalf
Date: Tue Jan 26 2016 - 12:22:56 EST

On 01/26/2016 12:04 PM, Jeff Merkey wrote:
This patch adds an export which can be set by system debuggers to direct
the hard lockup and soft lockup detector to trigger a breakpoint exception
and enter a debugger if one is active. It is assumed that if someone
sets this variable, then an breakpoint handler of some sort will be actively
loaded or registered via the notify die handler chain.

This addition is extremely useful for debugging hard and soft lockups
real time and quickly from a console debugger.

Signed-off-by: Jeff Merkey<linux.mdb@xxxxxxxxx>
kernel/watchdog.c | 10 ++++++++++
1 file changed, 10 insertions(+)

You probably should reach out to someone who uses this stuff more
regularly - I actually wonder if the kgdb_breakpoint() API is the
right thing, though, not the internal arch_kgdb_breakpoint().

Of course any of these strategies also assume you are building
the kernel with CONFIG_KGDB set, and I'm pretty sure will cause
your build to fail if it isn't. You likely need to guard this
stuff locally within watchdog.c for !CONFIG_KGDB.

Chris Metcalf, EZChip Semiconductor