[Adeos-main] [PATCH] avoid suboptimal use of ipipe_lock_cpu

[Jan Kiszka]

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

---
 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
===================================================================
--- 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;
 
-       ipipe_lock_cpu(flags);
+       local_irq_disable_hw();
+       ipipe_load_cpuid();
        __set_bit(IPIPE_STALL_FLAG, 
&__ipipe_pipeline_head()->cpudata[cpuid].status);
 }
 
 static inline unsigned long ipipe_test_and_stall_pipeline_head(void)
 {
-       unsigned long flags;
        ipipe_declare_cpuid;
 
-       ipipe_lock_cpu(flags);
+       local_irq_disable_hw();
+       ipipe_load_cpuid();
        return __test_and_set_bit(IPIPE_STALL_FLAG, 
&__ipipe_pipeline_head()->cpudata[cpuid].status);
 }
 
Index: linux-2.6.19/kernel/ipipe/core.c
===================================================================
--- 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;
 
-       ipipe_lock_cpu(flags);
+       local_irq_disable_hw();
+       ipipe_load_cpuid();
        head = __ipipe_pipeline_head();
        __clear_bit(IPIPE_STALL_FLAG, &head->cpudata[cpuid].status);
 
@@ -323,9 +323,9 @@ void ipipe_unstall_pipeline_head(void)
 void fastcall __ipipe_restore_pipeline_head(struct ipipe_domain *head, 
unsigned long x)
 {
        ipipe_declare_cpuid;
-       unsigned long flags;
 
-       ipipe_lock_cpu(flags);
+       local_irq_disable_hw();
+       ipipe_load_cpuid();
 
        if (x) {
 #ifdef CONFIG_DEBUG_KERNEL

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