linux-kernel - Re: [PATCH v4 13/13] riscv: Add qspinlock support

Open Source and information security mailing list archives

Message-ID: <0abc375c-61a1-4b8c-bac5-a5dc170c5fb6@ghiti.fr>
Date: Fri, 2 Aug 2024 10:58:51 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Andrew Jones <ajones@...tanamicro.com>,
 Alexandre Ghiti <alexghiti@...osinc.com>
Cc: Jonathan Corbet <corbet@....net>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
 Albert Ou <aou@...s.berkeley.edu>, Conor Dooley <conor@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Andrea Parri <parri.andrea@...il.com>, Nathan Chancellor
 <nathan@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
 Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>,
 Arnd Bergmann <arnd@...db.de>, Leonardo Bras <leobras@...hat.com>,
 Guo Ren <guoren@...nel.org>, linux-doc@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-riscv@...ts.infradead.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH v4 13/13] riscv: Add qspinlock support

On 01/08/2024 12:15, Andrew Jones wrote:
> On Thu, Aug 01, 2024 at 10:43:03AM GMT, Alexandre Ghiti wrote:
> ...
>>>> diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h
>>>> index 0655aa5b57b2..bf47cca2c375 100644
>>>> --- a/include/asm-generic/qspinlock.h
>>>> +++ b/include/asm-generic/qspinlock.h
>>>> @@ -136,6 +136,7 @@ static __always_inline bool virt_spin_lock(struct qspinlock *lock)
>>>>   }
>>>>   #endif
>>>>
>>>> +#ifndef __no_arch_spinlock_redefine
>>> I'm not sure what's better/worse, but instead of inventing this
>>> __no_arch_spinlock_redefine thing we could just name all the functions
>>> something like __arch_spin* and then add defines for both to asm/spinlock.h,
>>> i.e.
>>>
>>> #define queued_spin_lock(l) __arch_spin_lock(l)
>>> ...
>>>
>>> #define ticket_spin_lock(l) __arch_spin_lock(l)
>>> ...
>> __arch_spin_lock() would use queued_spin_lock() so that would make an
>> "infinite recursive definition" right? And that would override the
>> "real" queued_spin_lock() implementation too.
>>
>> But maybe I missed something!
>>
> It depends on where the definition is done. It should work if the
> preprocessor expands the implementation of __arch_spin_* before
> evaluating the #define of queued_spin_*. IOW, we just need to put
> the defines after the static inline constructions.

So I have just given it a try, both qspinlock.h and ticket_spinlock.h 
define arch_spin_XXXX(). That triggers a bunch of warnings.

I'll drop this suggestion as I find it harder to understand and because 
of the warnings that would need the introduction of a new preprocessor 
variable (or something else?).  And the solution with 
__no_arch_spinlock_redefine is really straightforward and lightweight.

Thanks,

Alex

>
> Thanks,
> drew
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives