From c14c338cb05c700a260480c197cfd6da8f8b7d2e Mon Sep 17 00:00:00 2001 From: Will Deacon <will.deacon@arm.com> Date: Wed, 11 Sep 2013 14:23:23 -0700 Subject: [PATCH] kernel/spinlock.c: add default arch_*_relax definitions for GENERIC_LOCKBREAK When running with GENERIC_LOCKBREAK=y, the locking implementations emit calls to arch_{read,write,spin}_relax when spinning on a contended lock in order to allow architectures to favour the CPU owning the lock if possible. In reality, everybody apart from PowerPC and S390 just does cpu_relax() here, so make that the default behaviour and allow it to be overridden if required. Signed-off-by: Will Deacon <will.deacon@arm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- kernel/spinlock.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/kernel/spinlock.c b/kernel/spinlock.c index 5cdd8065a3ce..4b082b5cac9e 100644 --- a/kernel/spinlock.c +++ b/kernel/spinlock.c @@ -34,6 +34,20 @@ #else #define raw_read_can_lock(l) read_can_lock(l) #define raw_write_can_lock(l) write_can_lock(l) + +/* + * Some architectures can relax in favour of the CPU owning the lock. + */ +#ifndef arch_read_relax +# define arch_read_relax(l) cpu_relax() +#endif +#ifndef arch_write_relax +# define arch_write_relax(l) cpu_relax() +#endif +#ifndef arch_spin_relax +# define arch_spin_relax(l) cpu_relax() +#endif + /* * We build the __lock_function inlines here. They are too large for * inlining all over the place, but here is only one user per function -- GitLab