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authorWill Deacon <will.deacon@arm.com>2013-09-11 14:23:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 15:58:21 -0700
commitc14c338cb05c700a260480c197cfd6da8f8b7d2e (patch)
tree1c6ed14664b122f57b4a75cfbad02ede7106f285 /kernel
parent60c323699bb308404dcb60e8808531e02651578a (diff)
downloadlinaro-lsk-c14c338cb05c700a260480c197cfd6da8f8b7d2e.tar.gz
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/spinlock.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index 5cdd8065a3c..4b082b5cac9 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