From: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
To: Dennis Zhou <dennis@kernel.org>
Cc: Christopher Lameter <cl@linux.com>,
Ben Dooks <ben.dooks@codethink.co.uk>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Tejun Heo <tj@kernel.org>, Nicholas Piggin <npiggin@gmail.com>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH] fix __percpu annotation in asm-generic
Date: Wed, 27 Nov 2019 23:54:32 +0100 [thread overview]
Message-ID: <20191127225432.ttwxm3hxtg5utfaz@ltop.local> (raw)
In-Reply-To: <20191127175350.GA52308@dennisz-mbp.dhcp.thefacebook.com>
On Wed, Nov 27, 2019 at 12:53:50PM -0500, Dennis Zhou wrote:
> On Wed, Nov 27, 2019 at 03:55:19PM +0000, Christopher Lameter wrote:
> > On Tue, 26 Nov 2019, Luc Van Oostenryck wrote:
> >
> > > So, fix the declaration of the 'pcp' variable to its correct type:
> > > the plain (non-percpu) pointer corresponding to its address.
> > > Same for raw_cpu_generic_xchg(), raw_cpu_generic_cmpxchg() &
> > > raw_cpu_generic_cmpxchg_double().
> >
> > Acked-by: Christoph Lameter <cl@linux.com>
> >
> > Maybe a better fix is to come up with a typeof_strip_percu() or so
> > macro for all the places where this needs to be done?
>
> I like the idea of typeof_strip_percpu(). Luc do you mind spinning v2
> with a macro for this instead?
I wouldn't mind at all (I already thought about doing something
like this several times) but:
1) it would strip any address space, not just __percpu, so:
it would need to be combined with __verify_pcpu_ptr() or,
* a better name should be used,
* it should be defined in a generic header, any idea where?
* I fear it would be abused to escape sloppy typing
(like __force and casts are already often used).
2) while I find the current solution:
typeof(T) __kernel __force *ptr = ...;
quite readable and relatively easy to understand, the solution
I have for doing it with a macro (that behaves like typeof) is,
IMO, much much less readable and understandable:
#define typeof_strip_percpu(T) \
typeof(({ typeof(T) __kernel __force __fakename; __fakename; }))
typeof_strip_perpcu(T) * ptr = ...;
So, if you insist I can do it but I would really prefer not.
Best regards,
-- Luc
next prev parent reply other threads:[~2019-11-27 22:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-26 20:06 [PATCH] fix __percpu annotation in asm-generic Luc Van Oostenryck
2019-11-27 15:55 ` Christopher Lameter
2019-11-27 17:53 ` Dennis Zhou
2019-11-27 22:54 ` Luc Van Oostenryck [this message]
2019-11-29 18:11 ` Christopher Lameter
2019-11-30 0:00 ` Luc Van Oostenryck
2019-12-02 19:07 ` Dennis Zhou
2019-12-02 19:42 ` Christopher Lameter
2019-12-03 3:01 ` Luc Van Oostenryck
2020-03-24 4:13 ` Jason A. Donenfeld
2020-03-24 6:44 ` Luc Van Oostenryck
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