[EDT][PATCH 1/1] hw_breakpoint.c :cpu hotplug handling

On Mon, May 18, 2015 at 05:46:31AM +0100, Vaneet Narang wrote:

EP-2DAD0AFA905A4ACB804C4F82A001242F

On Wed, May 13, 2015 at 06:24:06AM +0100, Maninder Singh wrote:

quoted

quoted

EP-2DAD0AFA905A4ACB804C4F82A001242F

Subject: [PATCH 1/1] hw_breakpoint.c :cpu hotplug handling

This patch adds support for CPU hotplug, It re-installl all installed watchpoints and breakpoints
back on H/W in case of cpu-hot plug.

quoted

Not sure why this is needed -- the scheduler should reinstall the
breakpoints when the debugged task gets scheduled in via
arch_install_hw_breakpoint.

Will

I agree with you this reinstalling has to be either take care by scheduler
or Debug tool. 

Which debug tool? If it's a ptrace user, then the scheduler should still
manage this, as ptrace will call into perf to create the breakpoints.

In current implementation we clear H/W registers but we don't clear slots
(wp_on_reg / bp_on_reg) for both watchpoint or breakpoint.

Ok, so are you saying that when the CPU is hotplugged off, the active
breakpoints aren't being uninstalled by perf? I thought this would have
happened as a result of the scheduler migrating the current task away
from the dying CPU.

Will