[Xen-devel] [PATCH][1/2] In cpufreq, check for a driver before use

[Mark Langsdorf <mark.langsdorf@xxxxxxx>]

The current cpufreq driver code assumes that a driver 
was registered before cpufreq_add_cpu() is called.  
If the driver was not registered or failed registration,
cpufreq_add_cpu() crashes.

Test to make sure that cpufreq_driver isn't NULL.

Signed-off-by: Mark Langsdorf <mark.langsdorf@xxxxxxx>

diff -r d7d7f978d704 xen/drivers/cpufreq/cpufreq.c
--- a/xen/drivers/cpufreq/cpufreq.c     Tue Oct 20 14:36:01 2009 +0100
+++ b/xen/drivers/cpufreq/cpufreq.c     Wed Oct 21 15:08:27 2009 -0500
@@ -142,6 +142,9 @@
         !(perf->init & XEN_PX_INIT) ||
         !cpu_online(cpu))
         return -EINVAL;
+
+    if (!cpufreq_driver)
+        return 0;
 
     if (cpufreq_cpu_policy[cpu])
         return 0;


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