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

From: Andrew Jones <ajones@ventanamicro.com>
To: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
	 Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Albert Ou <aou@eecs.berkeley.edu>,
	Conor Dooley <conor@kernel.org>, Rob Herring <robh@kernel.org>,
	 Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Andrea Parri <parri.andrea@gmail.com>,
	 Nathan Chancellor <nathan@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	 Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Waiman Long <longman@redhat.com>,
	 Boqun Feng <boqun.feng@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
	 Leonardo Bras <leobras@redhat.com>, Guo Ren <guoren@kernel.org>,
	linux-doc@vger.kernel.org,  devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	 linux-arch@vger.kernel.org
Subject: Re: [PATCH v4 13/13] riscv: Add qspinlock support
Date: Thu, 1 Aug 2024 12:15:00 +0200	[thread overview]
Message-ID: <20240801-e773d3752fe8b5484405d404@orel> (raw)
In-Reply-To: <CAHVXubhQefQ6i3Vow_p-uSACQyPcMJNC2UwB99xt_=jDtRUDFw@mail.gmail.com>

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.

Thanks,
drew