Messages in this thread | | | Subject | Re: [PATCH 2/2 v3] lib: debugobjects: touch watchdog to avoid softlockup when !CONFIG_PREEMPT | From | "Yang Shi" <> | Date | Thu, 18 Jan 2018 09:41:45 +0800 |
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On 1/17/18 4:21 AM, Thomas Gleixner wrote: > On Thu, 4 Jan 2018, Yang Shi wrote: > >> There are nested loops on debug objects free path, sometimes it may take >> over hundred thousands of loops, then cause soft lockup with !CONFIG_PREEMPT >> occasionally, like below: > > Please trim back traces. The whole module info and whatever is completely > irrelevant.
Yes, sure.
> >> @@ -768,6 +771,10 @@ static void __debug_check_no_obj_freed(const void *address, unsigned long size) >> debug_objects_maxchain = cnt; >> >> max_loops += cnt; >> + >> + if (max_loops > 10000 && ((max_loops % 10000) == 0) >> + && suppress_lockup != 0) >> + touch_softlockup_watchdog(); > > This is voodoo programming. > > There are two things which can be done here: > > 1) The collected objects can be put on a global free list and work > scheduled to free them piecewise.
I don't get your point here. objects free has already been done in a work. free_object() -> schedule_work()
Do you mean free all of them out of the for loop in a batch? Then don't call free_object() in the for loop?
> > 2) We can do a cond_resched() if not in atomic context and interrupts are > enabled.
I did try this before I went with touching softlockup watchdog approach. The problem is in_atomic() can't tell if it is in atomic context on non-preempt kernel. For preempt kernel, it is easy.
Thanks, Yang
> > I rather prefer to make that stuff robust than having crystal ball > constants and magic debugfs knobs. > > Thanks, > > tglx >
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