Messages in this thread | | | Date | Thu, 28 Jan 2016 16:15:02 +0900 | From | Byungchul Park <> | Subject | Re: [PATCH v4] lib/spinlock_debug.c: prevent a recursive cycle in the debug code |
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On Wed, Jan 27, 2016 at 02:49:35PM -0800, Peter Hurley wrote: > And we already have lockdep turned off to avoid triggering a recursive > lockdep report (which I think is a mistake).
Yes, we already have a way to turn off the lock debug so that we can avoid it. So I used it in v4.
thanks, byungchul
> > I think we should be working toward properly handling recursion > in printk(). > > Regards, > Peter Hurley > > > > When the debug spinlock code is called from printk(), we should prevent > > calling spin_dump() and the like, calling printk() again in that context. > > > > Signed-off-by: Byungchul Park <byungchul.park@lge.com> > > --- > > include/linux/debug_locks.h | 4 ++++ > > kernel/locking/spinlock_debug.c | 14 +++++++++++--- > > 2 files changed, 15 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h > > index 822c135..b0f977e 100644 > > --- a/include/linux/debug_locks.h > > +++ b/include/linux/debug_locks.h > > @@ -10,6 +10,10 @@ struct task_struct; > > extern int debug_locks; > > extern int debug_locks_silent; > > > > +static inline void __debug_locks_on(void) > > +{ > > + debug_locks = 1; > > +} > > > > static inline int __debug_locks_off(void) > > { > > diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c > > index 0374a59..65177ba 100644 > > --- a/kernel/locking/spinlock_debug.c > > +++ b/kernel/locking/spinlock_debug.c > > @@ -113,11 +113,19 @@ static void __spin_lock_debug(raw_spinlock_t *lock) > > return; > > __delay(1); > > } > > - /* lockup suspected: */ > > - spin_dump(lock, "lockup suspected"); > > + > > + /* > > + * We should prevent calling printk() further, since it would cause > > + * an infinite recursive cycle if it's called from printk()! > > + */ > > + if (__debug_locks_off()) { > > + /* lockup suspected: */ > > + spin_dump(lock, "lockup suspected"); > > #ifdef CONFIG_SMP > > - trigger_all_cpu_backtrace(); > > + trigger_all_cpu_backtrace(); > > #endif > > + __debug_locks_on(); > > + } > > > > /* > > * The trylock above was causing a livelock. Give the lower level arch > >
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