[Xen-changelog] [xen-unstable] trace: Do not touch percpu data for "impossible" cpus.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1273858742 -3600
# Node ID 44f25f7250bea0f14d90f4174f7cd337bc6215bf
# Parent  e95448fc993ed011bae65296a3f531798b128518
trace: Do not touch percpu data for "impossible" cpus.

While here, in fact only touch per-cpu data for online cpus. Use cpu
notifier chain to initialise per-cpu spinlock dynamically.

Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/common/trace.c |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)

diff -r e95448fc993e -r 44f25f7250be xen/common/trace.c
--- a/xen/common/trace.c        Fri May 14 18:25:55 2010 +0100
+++ b/xen/common/trace.c        Fri May 14 18:39:02 2010 +0100
@@ -29,6 +29,7 @@
 #include <xen/init.h>
 #include <xen/mm.h>
 #include <xen/percpu.h>
+#include <xen/cpu.h>
 #include <asm/atomic.h>
 #include <public/sysctl.h>
 
@@ -214,8 +215,6 @@ static int tb_set_size(int size)
      */
     int ret = 0;
 
-
-
     if ( (opt_tbuf_size != 0) )
     {
         if ( size != opt_tbuf_size )
@@ -269,6 +268,20 @@ int trace_will_trace_event(u32 event)
     return 1;
 }
 
+static int cpu_callback(
+    struct notifier_block *nfb, unsigned long action, void *hcpu)
+{
+    unsigned int cpu = (unsigned long)hcpu;
+
+    if ( action == CPU_UP_PREPARE )
+        spin_lock_init(&per_cpu(t_lock, cpu));
+
+    return NOTIFY_DONE;
+}
+
+static struct notifier_block cpu_nfb = {
+    .notifier_call = cpu_callback
+};
 /**
  * init_trace_bufs - performs initialization of the per-cpu trace buffers.
  *
@@ -289,8 +302,9 @@ void __init init_trace_bufs(void)
         return;
     }
 
-    for(i = 0; i < NR_CPUS; i++)
+    for_each_online_cpu ( i )
         spin_lock_init(&per_cpu(t_lock, i));
+    register_cpu_notifier(&cpu_nfb);
 
     for(i=0; i<T_INFO_PAGES; i++)
         share_xen_page_with_privileged_guests(

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