On Tue, 22 May 2018 12:53:53 +0530 Vaibhav Jain <vaib...@linux.vnet.ibm.com> wrote:
> Thanks for the patch Michal, > > Michal Suchanek <msucha...@suse.de> writes: > > > When single-stepping kernel code from xmon without a debug hook > > enabled the kernel crashes. This can happen when kernel starts with > > xmon on crash disabled but xmon is entered using sysrq. > > > > Commit e1368d0c9edb ("powerpc/xmon: Setup debugger hooks when first > > break-point is set") adds force_enable_xmon function that prints > > "xmon: Enabling debugger hooks" but does not enable them. > Debugger hooks are enabled just befores debugger() is entered from > sysrq_handle_xmon(). Thats why force_enable_xmon() simply sets sets > 'xmon_on=1' and exits. > > The problem you are seeing is probably due to sysrq_handle_xmon() > clearing the debugger hooks on return from debugger() as xmon_on was > never set for the 's' xmon command. Indeed, setting xmon_on is sufficient. Will resend the patch. Thanks Michal > > > Add the call to xmon_init to install the debugger hooks in > > force_enable_xmon and also call force_enable_xmon when > > single-stepping in xmon. > Only calling force_enable_xmon() from do_step() should be suffice as > on exit from the debugger() the value of xmon_on is checked and if > required the debugger hooks are kept instead of getting cleared. > > > > arch/powerpc/xmon/xmon.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c > > index a0842f1ff72c..504bd1c3d8b0 100644 > > --- a/arch/powerpc/xmon/xmon.c > > +++ b/arch/powerpc/xmon/xmon.c > > > > @@ -1275,6 +1279,7 @@ static inline void force_enable_xmon(void) > > if (!xmon_on) { > > printf("xmon: Enabling debugger hooks\n"); > > xmon_on = 1; > > + xmon_init(1); > > } > > } > > As mentioned above call to force_enable_xmon() is usually done in > context of sysrq_handle_xmon() which sets the debugger hooks as soon > as its entered. So I think that this hunk is not really needed. > >