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From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
	Davidlohr Bueso <davidlohr@hp.com>,
	Ingo Molnar <mingo@kernel.org>,
	Mikulas Patocka <mpatocka@redhat.com>,
	Jason Low <jason.low2@hp.com>, Waiman Long <waiman.long@hp.com>,
	"James E.J. Bottomley" <jejb@parisc-linux.org>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	John David Anglin <dave.anglin@bell.net>,
	"Chandramouleeswaran, Aswin" <aswin@hp.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Parisc List <linux-parisc@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	James Hogan <james.hogan@imgtec.com>,
	Chris Metcalf <cmetcalf@tilera.com>,
	Vineet Gupta <vgupta@synopsys.com>
Subject: Re: [PATCH 2/2] locking/rwsem: Disable optimistic spinning for PA-RISC
Date: Fri, 6 Jun 2014 19:53:16 +0200
Message-ID: <20140606175316.GV13930@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <CA+55aFxNLRufHyLHetnst7Lq0Ya1xoAagZf=DbEDTf1ZSfKFCQ@mail.gmail.com>

On Fri, Jun 06, 2014 at 10:22:21AM -0700, Linus Torvalds wrote:
> On Fri, Jun 6, 2014 at 10:11 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > +config ARCH_NO_ATOMIC_RMW
> > +       def_bool y
> > +       depends on PARISC || SPARC32 || METAG_ATOMICITY_LOCK1 || (TILE && !TILEGX) || (ARC && !ARC_HAS_LLSC)
> 
> Ugh. We've had these kinds of things before, and they are broken and
> nasty to maintain.
> 
> Just make it
> 
>     config ARCH_SUPPORTS_ATOMIC_RMW
>         bool
> 
> which defaults to no. And then make MUTEX_SPIN_ON_OWNER depend on that.

---
Subject: locking, mutex: Make optimistic spinning depend on ARCH_SUPPORTS_ATOMIC_RMW

The optimistic spin code assumes regular stores and cmpxchg() play nice;
this is found to not be true for at least: parisc, sparc32, tile32,
metag-lock1, arc-!llsc and hexagon.

There is further wreckage, but this in particular seemed easy to
trigger, so blacklist this.

Opt in for known good archs.

Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
 arch/arm/Kconfig     | 1 +
 arch/arm64/Kconfig   | 1 +
 arch/powerpc/Kconfig | 1 +
 arch/sparc/Kconfig   | 1 +
 arch/x86/Kconfig     | 1 +
 kernel/Kconfig.locks | 5 ++++-
 6 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a2c1a18a7275..b8a6a5078eae 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -6,6 +6,7 @@ config ARM
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_MIGHT_HAVE_PC_PARPORT
+	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_WANT_IPC_PARSE_VERSION
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 5c30b10c0f6c..339dc07f15e2 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -3,6 +3,7 @@ config ARM64
 	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
+	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 	select ARCH_WANT_FRAME_POINTERS
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e0998997943b..5bb96f282373 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -145,6 +145,7 @@ config PPC
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK
 	select ARCH_USE_CMPXCHG_LOCKREF if PPC64
 	select HAVE_ARCH_AUDITSYSCALL
+	select ARCH_SUPPORTS_ATOMIC_RMW
 
 config GENERIC_CSUM
 	def_bool CPU_LITTLE_ENDIAN
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 29f2e988c56a..407c87d9879a 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -78,6 +78,7 @@ config SPARC64
 	select HAVE_C_RECORDMCOUNT
 	select NO_BOOTMEM
 	select HAVE_ARCH_AUDITSYSCALL
+	select ARCH_SUPPORTS_ATOMIC_RMW
 
 config ARCH_DEFCONFIG
 	string
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3d4951d35587..2fe1f7c5994e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -130,6 +130,7 @@ config X86
 	select HAVE_CC_STACKPROTECTOR
 	select GENERIC_CPU_AUTOPROBE
 	select HAVE_ARCH_AUDITSYSCALL
+	select ARCH_SUPPORTS_ATOMIC_RMW
 
 config INSTRUCTION_DECODER
 	def_bool y
diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
index d2b32ac27a39..ecee67a00f5f 100644
--- a/kernel/Kconfig.locks
+++ b/kernel/Kconfig.locks
@@ -220,6 +220,9 @@ config INLINE_WRITE_UNLOCK_IRQRESTORE
 
 endif
 
+config ARCH_SUPPORTS_ATOMIC_RMW
+	bool
+
 config MUTEX_SPIN_ON_OWNER
 	def_bool y
-	depends on SMP && !DEBUG_MUTEXES
+	depends on SMP && !DEBUG_MUTEXES && ARCH_SUPPORTS_ATOMIC_RMW

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-06 15:55 [PATCH 0/2] locking/rwsem: disable " Davidlohr Bueso
2014-06-06 15:55 ` [PATCH 1/2] locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER Davidlohr Bueso
2014-06-06 17:13   ` Jason Low
2014-06-06 18:12     ` Davidlohr Bueso
2014-06-06 18:48       ` Davidlohr Bueso
2014-06-06 19:08         ` Jason Low
2014-06-06 19:20           ` Davidlohr Bueso
2014-06-06 15:55 ` [PATCH 2/2] locking/rwsem: Disable optimistic spinning for PA-RISC Davidlohr Bueso
2014-06-06 16:09   ` James Bottomley
2014-06-06 17:11     ` Peter Zijlstra
2014-06-06 17:19       ` Chris Metcalf
2014-06-06 17:22       ` Linus Torvalds
2014-06-06 17:53         ` Peter Zijlstra [this message]
2014-06-06 17:57           ` James Bottomley
2014-06-06 17:58             ` James Bottomley
2014-06-06 18:01             ` Peter Zijlstra

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