Update 2.6.36 to 2.6.36.4wip-dissipation2-jerickso

1 files changed, 37 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
index cf79b46d8f88..568b503d68bd 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -680,6 +680,13 @@ EXPORT_SYMBOL(arch_free_page);
 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
 extern long hcall_tracepoint_refcount;
 
+/*
+ * Since the tracing code might execute hcalls we need to guard against
+ * recursion. One example of this are spinlocks calling H_YIELD on
+ * shared processor partitions.
+ */
+static DEFINE_PER_CPU(unsigned int, hcall_trace_depth);
+
 void hcall_tracepoint_regfunc(void)
 {
         hcall_tracepoint_refcount++;
@@ -692,12 +699,42 @@ void hcall_tracepoint_unregfunc(void)
 
 void __trace_hcall_entry(unsigned long opcode, unsigned long *args)
 {
+        unsigned long flags;
+        unsigned int *depth;
+
+        local_irq_save(flags);
+
+        depth = &__get_cpu_var(hcall_trace_depth);
+
+        if (*depth)
+                goto out;
+
+        (*depth)++;
         trace_hcall_entry(opcode, args);
+        (*depth)--;
+
+out:
+        local_irq_restore(flags);
 }
 
 void __trace_hcall_exit(long opcode, unsigned long retval,
                         unsigned long *retbuf)
 {
+        unsigned long flags;
+        unsigned int *depth;
+
+        local_irq_save(flags);
+
+        depth = &__get_cpu_var(hcall_trace_depth);
+
+        if (*depth)
+                goto out;
+
+        (*depth)++;
         trace_hcall_exit(opcode, retval, retbuf);
+        (*depth)--;
+
+out:
+        local_irq_restore(flags);
 }
 #endif