Andrea Parri c6f5d02b6a locking/spinlocks/arm64: Remove smp_mb() from arch_spin_is_locked() ... The following commit: 38b850a730 ("arm64: spinlock: order spin_{is_locked,unlock_wait} against local locks") ... added an smp_mb() to arch_spin_is_locked(), in order "to ensure that the lock value is always loaded after any other locks have been taken by the current CPU", and reported one example (the "insane case" in ipc/sem.c) relying on such guarantee. It is however understood that spin_is_locked() is not required to provide such an ordering guarantee (a guarantee that is currently not provided by all the implementations/archs), and that callers relying on such ordering should instead insert suitable memory barriers before acting on the result of spin_is_locked(). Following a recent auditing [1] of the callers of {,raw_}spin_is_locked(), revealing that none of them are relying on the ordering guarantee anymore, this commit removes the leading smp_mb() from the primitive thus reverting 38b850a730. [1] https://marc.info/?l=linux-kernel&m=151981440005264&w=2 https://marc.info/?l=linux-kernel&m=152042843808540&w=2 https://marc.info/?l=linux-kernel&m=152043346110262&w=2 Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Will Deacon <will.deacon@arm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akiyks@gmail.com Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Link: http://lkml.kernel.org/r/1526338889-7003-2-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>		2018-05-15 08:11:15 +02:00
..
boot	This pull request contains Broadcom ARM64-based SoCs Device Tree fixes	2018-04-27 10:21:18 +02:00
configs	arm64: defconfig: add CONFIG_UNIPHIER_THERMAL and CONFIG_SNI_AVE	2018-03-27 15:31:19 +02:00
crypto	kbuild: mark $(targets) as .SECONDARY and remove .PRECIOUS markers	2018-04-07 19:04:02 +09:00
include	locking/spinlocks/arm64: Remove smp_mb() from arch_spin_is_locked()	2018-05-15 08:11:15 +02:00
kernel	arm64: capabilities: Add NVIDIA Denver CPU to bp_harden list	2018-05-09 14:28:28 +01:00
kvm	arm64: vgic-v2: Fix proxying of cpuif access	2018-05-04 16:45:55 +01:00
lib	arm64: avoid instrumenting atomic_ll_sc.o	2018-04-27 12:14:44 +01:00
mm	arm64: To remove initrd reserved area entry from memblock	2018-05-01 10:19:30 +01:00
net	bpf, arm64: fix out of bounds access in tail call	2018-02-22 16:06:28 -08:00
xen	arm64: mm: Add additional parameter to uaccess_ttbr0_disable	2018-01-17 13:57:49 +01:00
Kconfig	ARM:	2018-04-09 11:42:31 -07:00
Kconfig.debug	arm64: relocation testing module	2017-04-04 17:03:32 +01:00
Kconfig.platforms	arm64: add Renesas R8A77965 support	2018-03-13 19:05:58 +01:00
Makefile	arm64: support __int128 with clang	2018-04-24 19:07:55 +01:00