Messages in this thread | | | Subject | Re: [PATCH 2/2] debugobjects: Print warnings outside bucket lock | From | Waiman Long <> | Date | Thu, 13 Dec 2018 17:04:13 -0500 |
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On 12/12/2018 11:34 PM, Dmitry Safonov wrote: > Whenever debugobjects finds invalid pattern during life time of a kernel > object such as: > - Activation of uninitialized objects > - Initialization of active objects > - Usage of freed/destroyed objects > it prints a warning and tries to make fixup over an object. > > Unfortunately, it becomes error-prone to use WARN() or printing under > debugobjects bucket lock: printk() may defer work to workqueue, and > realization of workqueues uses debugobjects. Further, console drivers > use page allocator, potentially vmalloc() or slub/slab. Which reasonably > makes lockdep to go nuts as there are debug_check_no_obj_freed() checks > in allocators. > > Move printings out of debugobjets bucket lock to address the potential > lockups. > > Link: lkml.kernel.org/r/20181211091154.GL23332@shao2-debian > Reported-by: kernel test robot <rong.a.chen@intel.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Waiman Long <longman@redhat.com> > Signed-off-by: Dmitry Safonov <dima@arista.com> > --- > lib/debugobjects.c | 89 ++++++++++++++++++++++++---------------------- > 1 file changed, 47 insertions(+), 42 deletions(-) > > diff --git a/lib/debugobjects.c b/lib/debugobjects.c > index 98968219405b..0c92e46cb588 100644 > --- a/lib/debugobjects.c > +++ b/lib/debugobjects.c > @@ -313,7 +313,7 @@ static struct debug_bucket *get_bucket(unsigned long addr) > return &obj_hash[hash]; > } > > -static void debug_print_object(struct debug_obj *obj, char *msg) > +static void __debug_print_object(struct debug_obj *obj, char *msg) > { > struct debug_obj_descr *descr = obj->descr; > static int limit; > @@ -330,6 +330,14 @@ static void debug_print_object(struct debug_obj *obj, char *msg) > debug_objects_warnings++; > } > > +#define debug_print_object(obj, msg, lock, flags) \ > + do { \ > + struct debug_obj tmp = *obj; \ > + \ > + raw_spin_unlock_irqrestore(lock, flags); \ > + __debug_print_object(&tmp, msg); \ > + } while(0) > +
My main problem with this patch is the hiding of the unlock call in the macro. I will prefer matching unlocks to be clearly visible in the function bodies. Otherwise, the readers may be confused.
Cheers, Longman
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