Messages in this thread | | | From | Sumit Garg <> | Date | Tue, 26 May 2020 13:27:28 +0530 | Subject | Re: [PATCH v2] kdb: Make kdb_printf robust to run in NMI context |
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On Fri, 22 May 2020 at 22:05, Daniel Thompson <daniel.thompson@linaro.org> wrote: > > On Fri, May 22, 2020 at 08:03:47PM +0530, Sumit Garg wrote: > > While rounding up CPUs via NMIs, its possible that a rounded up CPU > > maybe holding a console port lock leading to kgdb master CPU stuck in > > a deadlock during invocation of console write operations. So in order > > to avoid such a deadlock, invoke bust_spinlocks() prior to invocation > > of console handlers. > > > > Also, add a check for console port to be enabled prior to invocation of > > corresponding handler. > > Perhaps this should have been two patches. >
Okay, will split this patch into two.
> In fact, to be honest, I'd suggest combining all the patches to improve > kdb console handling (including a fixed version of the RFC) into a > single patch set.
Yeah it makes sense to have a combined patch set to improve kdb console handling. But I posted the RFC patch separately as I expected comments and discussions to come up with an accepted approach.
So let me wait for an agreement on RFC patch after which I can include that patch in this patch set.
> > > > Suggested-by: Petr Mladek <pmladek@suse.com> > > Suggested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > > --- > > > > Changes in v2: > > - Use oops_in_progress directly instead of bust_spinlocks(). > > > > kernel/debug/kdb/kdb_io.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c > > index 924bc92..3a5a068 100644 > > --- a/kernel/debug/kdb/kdb_io.c > > +++ b/kernel/debug/kdb/kdb_io.c > > @@ -699,7 +699,11 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) > > } > > } > > for_each_console(c) { > > + if (!(c->flags & CON_ENABLED)) > > + continue; > > + ++oops_in_progress; > > Given the subtly of what is going on I think we need some comments in > the code on what we are doing and why.
Sure, will add comments.
> > > > c->write(c, cp, retlen - (cp - kdb_buffer)); > > + --oops_in_progress; > > touch_nmi_watchdog(); > > } > > } > > @@ -761,7 +765,11 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) > > } > > } > > for_each_console(c) { > > + if (!(c->flags & CON_ENABLED)) > > + continue; > > + ++oops_in_progress; > > c->write(c, moreprompt, strlen(moreprompt)); > > + --oops_in_progress; > > touch_nmi_watchdog(); > > As with the other patches maybe the first patch in the set should be > factoring out the common code before making changes to it.
Sure, will factor out common code as initial patch.
-Sumit
> > > Daniel.
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