Messages in this thread | | | Date | Wed, 17 Jan 2018 13:21:45 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 2/2 v3] lib: debugobjects: touch watchdog to avoid softlockup when !CONFIG_PREEMPT |
| |
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.
> @@ -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.
2) We can do a cond_resched() if not in atomic context and interrupts are enabled.
I rather prefer to make that stuff robust than having crystal ball constants and magic debugfs knobs.
Thanks,
tglx
| |