On Wed, Oct 18, 2017 at 03:36:05PM +0200, Thomas Gleixner wrote: > On Wed, 18 Oct 2017, Ingo Molnar wrote: > > * Thomas Gleixner <t...@linutronix.de> wrote: > > > > > On Wed, 18 Oct 2017, Byungchul Park wrote: > > > > #ifdef CONFIG_LOCKDEP_CROSSRELEASE > > > > +#ifdef CONFIG_CROSSRELEASE_STACK_TRACE > > > > #define MAX_XHLOCK_TRACE_ENTRIES 5 > > > > +#else > > > > +#define MAX_XHLOCK_TRACE_ENTRIES 1 > > > > +#endif > > > > > > > > /* > > > > * This is for keeping locks waiting for commit so that true > > > > dependencies > > > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > > > > index e36e652..5c2ddf2 100644 > > > > --- a/kernel/locking/lockdep.c > > > > +++ b/kernel/locking/lockdep.c > > > > @@ -4863,8 +4863,13 @@ static void add_xhlock(struct held_lock *hlock) > > > > xhlock->trace.nr_entries = 0; > > > > xhlock->trace.max_entries = MAX_XHLOCK_TRACE_ENTRIES; > > > > xhlock->trace.entries = xhlock->trace_entries; > > > > +#ifdef CONFIG_CROSSRELEASE_STACK_TRACE > > > > xhlock->trace.skip = 3; > > > > save_stack_trace(&xhlock->trace); > > > > +#else > > > > + xhlock->trace.nr_entries = 1; > > > > + xhlock->trace.entries[0] = hlock->acquire_ip; > > > > +#endif > > > > > > Hmm. Would it be possible to have this switchable at boot time via a > > > command line parameter? So in case of a splat with no stack trace, one > > > could just reboot and set something like 'lockdep_fullstack' on the kernel > > > command line to get the full data without having to recompile the kernel. > > > > Yeah, and I'd suggest keeping the Kconfig option to default-enable that > > boot > > option as well - i.e. let's have both. > > That makes sense. Like we have with debug objects: > DEBUG_OBJECTS_ENABLE_DEFAULT.
Thank you very much for the suggestion. I will work for it. > Which reminds me that I wanted to convert them to static_key so they are > zero overhead when disabled. Sigh, why are todo lists growth only? > > Thanks, > > tglx
