Re: [PATCH 3/5] openrisc: Move to ticket-spinlock

From: Stafford Horne <shorne@gmail.com>
To: Guo Ren <guoren@kernel.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Jonas Bonn <jonas@southpole.se>,
	Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de>,
	jszhang@kernel.org, Kefeng Wang <wangkefeng.wang@huawei.com>,
	Openrisc <openrisc@lists.librecores.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH 3/5] openrisc: Move to ticket-spinlock
Date: Tue, 22 Mar 2022 13:10:08 +0900	[thread overview]
Message-ID: <YjlMIGKgYaLLpp5T@antec> (raw)
In-Reply-To: <CAJF2gTSFh0NKLys7kr=UdQWHDyYgg3XmgTJtVaL37Re7QdZ8uw@mail.gmail.com>

On Tue, Mar 22, 2022 at 11:29:13AM +0800, Guo Ren wrote:
> On Tue, Mar 22, 2022 at 7:23 AM Stafford Horne <shorne@gmail.com> wrote:
> >
> > On Wed, Mar 16, 2022 at 04:25:58PM -0700, Palmer Dabbelt wrote:
> > > From: Peter Zijlstra <peterz@infradead.org>
> > >
> > > We have no indications that openrisc meets the qspinlock requirements,
> > > so move to ticket-spinlock as that is more likey to be correct.
> > >
> > > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> > >
> > > ---
> > >
> > > I have specifically not included Peter's SOB on this, as he sent his
> > > original patch
> > > <https://lore.kernel.org/lkml/YHbBBuVFNnI4kjj3@hirez.programming.kicks-ass.net/>
> > > without one.
> > > ---
> > >  arch/openrisc/Kconfig                      | 1 -
> > >  arch/openrisc/include/asm/Kbuild           | 5 ++---
> > >  arch/openrisc/include/asm/spinlock.h       | 3 +--
> > >  arch/openrisc/include/asm/spinlock_types.h | 2 +-
> > >  4 files changed, 4 insertions(+), 7 deletions(-)
> >
> > Hello,
> >
> > This series breaks SMP support on OpenRISC.  I haven't traced it down yet, it
> > seems trivial but I have a few places to check.
> >
> > I replied to this on a kbuild warning thread, but also going to reply here with
> > more information.
> >
> >  https://lore.kernel.org/lkml/YjeY7CfaFKjr8IUc@antec/#R
> >
> > So far this is what I see:
> >
> >   * ticket_lock is stuck trying to lock console_sem
> >   * it is stuck on atomic_cond_read_acquire
> >     reading lock value: returns 0    (*lock is 0x10000)
> >     ticket value: is 1
> >   * possible issues:
> >     - OpenRISC is big endian, that seems to impact ticket_unlock, it looks
> All csky & riscv are little-endian, it seems the series has a bug with
> big-endian. Is that all right for qemu? (If qemu was all right, but
> real hardware failed.)

Hi Guo Ren,

OpenRISC real hardware and QEMU are both big-endian.  It fails on both.

I replied on patch 1/5 with a suggested patch which fixes the issue for me.
Please have a look.

BTW. now I can look into the sparse warnings.

-Stafford