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Date: Mon, 25 Oct 2021 11:57:28 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Arnd Bergmann <arnd@...nel.org> Cc: Waiman Long <longman@...hat.com>, Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>, Boqun Feng <boqun.feng@...il.com>, Jonas Bonn <jonas@...thpole.se>, Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>, Stafford Horne <shorne@...il.com>, "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>, Helge Deller <deller@....de>, Michael Ellerman <mpe@...erman.id.au>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-ia64@...r.kernel.org, Openrisc <openrisc@...ts.librecores.org>, Parisc List <linux-parisc@...r.kernel.org>, linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, linux-s390 <linux-s390@...r.kernel.org> Subject: Re: [PATCH] locking: remove spin_lock_flags() etc On Sat, Oct 23, 2021 at 06:04:57PM +0200, Arnd Bergmann wrote: > On Sat, Oct 23, 2021 at 3:37 AM Waiman Long <longman@...hat.com> wrote: > >> On 10/22/21 7:59 AM, Arnd Bergmann wrote: > > > From: Arnd Bergmann <arnd@...db.de> > > > > > > As this is all dead code, just remove it and the helper functions built > > > around it. For arch/ia64, the inline asm could be cleaned up, but > > > it seems safer to leave it untouched. > > > > > > Signed-off-by: Arnd Bergmann <arnd@...db.de> > > > > Does that mean we can also remove the GENERIC_LOCKBREAK config option > > from the Kconfig files as well? > > I couldn't figure this out. > > What I see is that the only architectures setting GENERIC_LOCKBREAK are > nds32, parisc, powerpc, s390, sh and sparc64, while the only architectures > implementing arch_spin_is_contended() are arm32, csky and ia64. > > The part I don't understand is whether the option actually does anything > useful any more after commit d89c70356acf ("locking/core: Remove break_lock > field when CONFIG_GENERIC_LOCKBREAK=y"). Urgh, what a mess.. AFAICT there's still code in kernel/locking/spinlock.c that relies on it. Specifically when GENERIC_LOCKBREAK=y we seem to create _lock*() variants that are basically TaS locks which drop preempt/irq disable while spinning. Anybody having this on and not having native TaS locks is in for a rude surprise I suppose... sparc64 being the obvious candidate there :/
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