Re: [PRE-REVIEW PATCH 00/16] Modernize the tasklet API

From: Kees Cook <keescook@chromium.org>
To: Romain Perier <romain.perier@gmail.com>
Cc: Allen <allen.lkml@gmail.com>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>
Subject: Re: [PRE-REVIEW PATCH 00/16] Modernize the tasklet API
Date: Thu, 7 Nov 2019 13:22:21 -0800	[thread overview]
Message-ID: <201911071321.8A2A664B4A@keescook> (raw)
In-Reply-To: <CABgxDoLbEci9oS3sAmuiZdbBjgxEVbrnrpiqO64zfZDMCF9fvw@mail.gmail.com>

On Thu, Nov 07, 2019 at 08:29:40AM +0100, Romain Perier wrote:
> Le mer. 30 oct. 2019 à 09:21, Allen <allen.lkml@gmail.com> a écrit :
> >
> > Romain,
> > >
> >
> >  First of all Romain, nice work. I started working on this
> > set a few months back, but could only carve out limited time.
> >
> >   I sent out RFC for this sometime in May[1]. And my approach
> > was a little different when compared to what you have sent on the
> > list.
> >
> >  Well, I have pushed my work to github[2], only thing I could
> > think of as an improvement in your patch set it to break it down
> > into smaller chunk so that it's easier to review. I have made each
> > occurrence of tasklet_init() into a commit[3] which I thought would
> > make it easier to review. I'll leave that decision to you and kees.
> >
> > Let me know if I could help in any way.
> >
> > [1] https://www.openwall.com/lists/kernel-hardening/2019/05/06/1
> > [2] https://github.com/allenpais/tasklet
> > [3] Sample list of patches:
> > 5d0b728649b6 atm/solos-pci: Convert tasklets to use new tasklet_init API
> > e5144c3c16d8 atm: Convert tasklets to use new tasklet_init API
> > 71028976d3ed arch/um: Convert tasklets to use new tasklet_init API
> > c9a39c23b78c xfrm: Convert tasklets to use new tasklet_init API
> > 91d93fe12bbc mac80211: Convert tasklets to use new tasklet_init API
> > d68f1e9e4531 ipv4: Convert tasklets to use new tasklet_init API
> > 4f9379dcd8ad sound/timer: Convert tasklets to use new tasklet_init API
> > b4519111b75e drivers/usb: Convert tasklets to use new tasklet_init API
> > 52f04bf54a5a drivers:vt/keyboard: Convert tasklets to use new tasklet_init API
> > 295de7c9812c dma/virt-dma: Convert tasklets to use new tasklet_init API
> > 6c713c83b58f dma/dw: Convert tasklets to use new tasklet_init API
> > eaaaaba8a4a7 debug:Convert tasklets to use new tasklet_init API
> > b23f4ff5021b tasklet: prepare to change tasklet API
> 
> From experience, this is better to group bunch of commits like we
> currently do with Kees on this series, instead to have one commit per
> change (I mean for huge patchset)
> Mainly because you have too much replacements with this API change,
> and it will be really complicated to merge.
> 
> Last time I have proposed an API change for removing "pci_pool" , it
> was a patchset of 20 commits (something like this), it tooks 6 months
> to be merged :) (with a fine grain granularity on each commit)
> 
> This is better to be the more atomic as possible. If we split the "one
> massive tasklet_init replacement" commit into many commit, I am sure
> that we find old tasklet API for months in the kernel... it is not
> something we want , imho.  + treewide commits are common in the kernel
> tree, for important API changes :)
> 
> @Kees: agreed ?
> 
> I think that the timer_list approach is good. You can help by
> providing feedbacks and by testing if you want.

It worked well the last time. :)

I think splitting the non-mechanical changes and landing those first is
the right approach. Then we can land a massive treewide for all the
"easy" cases without trickling them in over months.

-Kees

-- 
Kees Cook