From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Wed, 13 Dec 2006 18:58:12 +0100
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: [Adeos-main] [PATCH] avoid suboptimal use of ipipe_lock_cpu
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Hi,

while disassembling that bug in start_kernel, I noticed that
ipipe_lock_cpu(flags) is used in a suboptimal way in some
ipipe_XXX_head() services, i.e. when the flags are actually of no
interest. The compiler still generates the unneeded pushf/pop <reg>, and
this in a hot-path.

Attached patch should perform better. Lightly tested, but QEMU SMP still
works here.

Jan

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 name="avoid-ipipe_lock_cpu.patch"
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 filename="avoid-ipipe_lock_cpu.patch"

---
 include/linux/ipipe.h |    8 ++++----
 kernel/ipipe/core.c   |    8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

Index: linux-2.6.19/include/linux/ipipe.h
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- linux-2.6.19.orig/include/linux/ipipe.h
+++ linux-2.6.19/include/linux/ipipe.h
@@ -471,18 +471,18 @@ static inline void ipipe_restore_pipelin
 static inline void ipipe_stall_pipeline_head(void)
 {
 	ipipe_declare_cpuid;
-	unsigned long flags;
=20
-	ipipe_lock_cpu(flags);
+	local_irq_disable_hw();
+	ipipe_load_cpuid();
 	__set_bit(IPIPE_STALL_FLAG, &__ipipe_pipeline_head()->cpudata[cpuid].st=
atus);
 }
=20
 static inline unsigned long ipipe_test_and_stall_pipeline_head(void)
 {
-	unsigned long flags;
 	ipipe_declare_cpuid;
=20
-	ipipe_lock_cpu(flags);
+	local_irq_disable_hw();
+	ipipe_load_cpuid();
 	return __test_and_set_bit(IPIPE_STALL_FLAG, &__ipipe_pipeline_head()->c=
pudata[cpuid].status);
 }
=20
Index: linux-2.6.19/kernel/ipipe/core.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- linux-2.6.19.orig/kernel/ipipe/core.c
+++ linux-2.6.19/kernel/ipipe/core.c
@@ -303,10 +303,10 @@ void fastcall ipipe_restore_pipeline_fro
 void ipipe_unstall_pipeline_head(void)
 {
 	struct ipipe_domain *head;
-	unsigned long flags;
 	ipipe_declare_cpuid;
=20
-	ipipe_lock_cpu(flags);
+	local_irq_disable_hw();
+	ipipe_load_cpuid();
 	head =3D __ipipe_pipeline_head();
 	__clear_bit(IPIPE_STALL_FLAG, &head->cpudata[cpuid].status);
=20
@@ -323,9 +323,9 @@ void ipipe_unstall_pipeline_head(void)
 void fastcall __ipipe_restore_pipeline_head(struct ipipe_domain *head, u=
nsigned long x)
 {
 	ipipe_declare_cpuid;
-	unsigned long flags;
=20
-	ipipe_lock_cpu(flags);
+	local_irq_disable_hw();
+	ipipe_load_cpuid();
=20
 	if (x) {
 #ifdef CONFIG_DEBUG_KERNEL

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