Messages in this thread | | | Date | Thu, 15 Aug 2019 22:00:36 -0300 | From | Jason Gunthorpe <> | Subject | Re: [Intel-gfx] [PATCH 2/5] kernel.h: Add non_block_start/end() |
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On Thu, Aug 15, 2019 at 10:49:31PM +0200, Daniel Vetter wrote: > On Thu, Aug 15, 2019 at 10:27 PM Jason Gunthorpe <jgg@ziepe.ca> wrote: > > On Thu, Aug 15, 2019 at 10:16:43PM +0200, Daniel Vetter wrote: > > > So if someone can explain to me how that works with lockdep I can of > > > course implement it. But afaics that doesn't exist (I tried to explain > > > that somewhere else already), and I'm no really looking forward to > > > hacking also on lockdep for this little series. > > > > Hmm, kind of looks like it is done by calling preempt_disable() > > Yup. That was v1, then came the suggestion that disabling preemption > is maybe not the best thing (the oom reaper could still run for a long > time comparatively, if it's cleaning out gigabytes of process memory > or what not, hence this dedicated debug infrastructure).
Oh, I'm coming in late, sorry
Anyhow, I was thinking since we agreed this can trigger on some CONFIG_DEBUG flag, something like
/* This is a sleepable region, but use preempt_disable to get debugging * for calls that are not allowed to block for OOM [.. insert * Michal's explanation.. ] */ if (IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP) && !mmu_notifier_range_blockable(range)) preempt_disable(); ops->invalidate_range_start();
And I have also been idly mulling doing something like
if (IS_ENABLED(CONFIG_DEBUG_NOTIFIERS) && rand && mmu_notifier_range_blockable(range)) { range->flags = 0 if (!ops->invalidate_range_start(range)) continue
// Failed, try again as blockable range->flags = MMU_NOTIFIER_RANGE_BLOCKABLE } ops->invalidate_range_start(range);
Which would give coverage for this corner case without forcing OOM.
Jason
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