From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by kanga.kvack.org (Postfix) with ESMTP id 0E0446B4653 for ; Tue, 27 Nov 2018 11:50:17 -0500 (EST) Received: by mail-wm1-f70.google.com with SMTP id f193so18179252wme.8 for ; Tue, 27 Nov 2018 08:50:17 -0800 (PST) Received: from fireflyinternet.com (mail.fireflyinternet.com. [109.228.58.192]) by mx.google.com with ESMTPS id c6si3788769wrw.25.2018.11.27.08.50.15 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Nov 2018 08:50:15 -0800 (PST) Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable From: Chris Wilson In-Reply-To: <20181127074918.GT4266@phenom.ffwll.local> References: <20181122165106.18238-1-daniel.vetter@ffwll.ch> <20181122165106.18238-4-daniel.vetter@ffwll.ch> <20181127074918.GT4266@phenom.ffwll.local> Message-ID: <154333737908.11623.17864230889834398136@skylake-alporthouse-com> Subject: Re: [Intel-gfx] [PATCH 3/3] mm, notifier: Add a lockdep map for invalidate_range_start Date: Tue, 27 Nov 2018 16:49:39 +0000 Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Vetter , LKML Cc: Michal Hocko , Greg Kroah-Hartman , Daniel Vetter , Intel Graphics Development , DRI Development , Linux MM , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Mike Rapoport , David Rientjes , Daniel Vetter , Andrew Morton , =?utf-8?q?Christian_K=C3=B6nig?= Quoting Daniel Vetter (2018-11-27 07:49:18) > On Thu, Nov 22, 2018 at 05:51:06PM +0100, Daniel Vetter wrote: > > This is a similar idea to the fs_reclaim fake lockdep lock. It's > > fairly easy to provoke a specific notifier to be run on a specific > > range: Just prep it, and then munmap() it. > > = > > A bit harder, but still doable, is to provoke the mmu notifiers for > > all the various callchains that might lead to them. But both at the > > same time is really hard to reliable hit, especially when you want to > > exercise paths like direct reclaim or compaction, where it's not > > easy to control what exactly will be unmapped. > > = > > By introducing a lockdep map to tie them all together we allow lockdep > > to see a lot more dependencies, without having to actually hit them > > in a single challchain while testing. > > = > > Aside: Since I typed this to test i915 mmu notifiers I've only rolled > > this out for the invaliate_range_start callback. If there's > > interest, we should probably roll this out to all of them. But my > > undestanding of core mm is seriously lacking, and I'm not clear on > > whether we need a lockdep map for each callback, or whether some can > > be shared. > > = > > Cc: Andrew Morton > > Cc: David Rientjes > > Cc: "J=C3=A9r=C3=B4me Glisse" > > Cc: Michal Hocko > > Cc: "Christian K=C3=B6nig" > > Cc: Greg Kroah-Hartman > > Cc: Daniel Vetter > > Cc: Mike Rapoport > > Cc: linux-mm@kvack.org > > Signed-off-by: Daniel Vetter > = > Any comments on this one here? This is really the main ingredient for > catching deadlocks in mmu notifier callbacks. The other two patches are > more the icing on the cake. > = > Thanks, Daniel > = > > --- > > include/linux/mmu_notifier.h | 7 +++++++ > > mm/mmu_notifier.c | 7 +++++++ > > 2 files changed, 14 insertions(+) > > = > > diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h > > index 9893a6432adf..a39ba218dbbe 100644 > > --- a/include/linux/mmu_notifier.h > > +++ b/include/linux/mmu_notifier.h > > @@ -12,6 +12,10 @@ struct mmu_notifier_ops; > > = > > #ifdef CONFIG_MMU_NOTIFIER > > = > > +#ifdef CONFIG_LOCKDEP > > +extern struct lockdep_map __mmu_notifier_invalidate_range_start_map; > > +#endif > > + > > /* > > * The mmu notifier_mm structure is allocated and installed in > > * mm->mmu_notifier_mm inside the mm_take_all_locks() protected > > @@ -267,8 +271,11 @@ static inline void mmu_notifier_change_pte(struct = mm_struct *mm, > > static inline void mmu_notifier_invalidate_range_start(struct mm_struc= t *mm, > > unsigned long start, unsigned long end) > > { > > + mutex_acquire(&__mmu_notifier_invalidate_range_start_map, 0, 0, > > + _RET_IP_); Would not lock_acquire_shared() be more appropriate, i.e. treat this as a rwsem_acquire_read()? -Chris