Subject: + kernel-spinlockc-add-default-arch__relax-definitions-for-generic_lockbreak.patch added to -mm tree
To: will.deacon@xxxxxxx,benh@xxxxxxxxxxxxxxxxxxx,mingo@xxxxxxx,schwidefsky@xxxxxxxxxx,tglx@xxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 26 Jul 2013 13:30:03 -0700
The patch titled
Subject: kernel/spinlock.c: add default arch_*_relax definitions for GENERIC_LOCKBREAK
has been added to the -mm tree. Its filename is
kernel-spinlockc-add-default-arch__relax-definitions-for-generic_lockbreak.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-spinlockc-add-default-arch__relax-definitions-for-generic_lockbreak.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-spinlockc-add-default-arch__relax-definitions-for-generic_lockbreak.patch
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------------------------------------------------------
From: Will Deacon <will.deacon@xxxxxxx>
Subject: 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@xxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/spinlock.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff -puN kernel/spinlock.c~kernel-spinlockc-add-default-arch__relax-definitions-for-generic_lockbreak kernel/spinlock.c
--- a/kernel/spinlock.c~kernel-spinlockc-add-default-arch__relax-definitions-for-generic_lockbreak
+++ a/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
_
Patches currently in -mm which might be from will.deacon@xxxxxxx are
origin.patch
kernel-spinlockc-add-default-arch__relax-definitions-for-generic_lockbreak.patch
linux-next.patch
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