x86, bts: remove recursion from get_context

Impact: cleanup

Optimistically allocate a DS context. It is extremely unlikely that
one already existed. This simplifies the code a lot.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 25 insertions, 33 deletions

diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index dc1e7123ea4e..0dc795951d73 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -232,53 +232,45 @@ static DEFINE_PER_CPU(struct ds_context *, system_context_array);
 
 #define system_context per_cpu(system_context_array, smp_processor_id())
 
-static struct ds_context *ds_get_context(struct task_struct *task)
+
+static inline struct ds_context *ds_get_context(struct task_struct *task)
 {
         struct ds_context **p_context =
                 (task ? &task->thread.ds_ctx : &system_context);
-        struct ds_context *context = *p_context;
+        struct ds_context *context = NULL;
+        struct ds_context *new_context = NULL;
         unsigned long irq;
 
-        if (!context) {
-                context = kzalloc(sizeof(*context), GFP_KERNEL);
-                if (!context)
-                        return NULL;
-
-                spin_lock_irqsave(&ds_lock, irq);
-
-                if (*p_context) {
-                        kfree(context);
+        /* Chances are small that we already have a context. */
+        new_context = kzalloc(sizeof(*new_context), GFP_KERNEL);
+        if (!new_context)
+                return NULL;
 
-                        context = *p_context;
-                } else {
-                        *p_context = context;
+        spin_lock_irqsave(&ds_lock, irq);
 
-                        context->this = p_context;
-                        context->task = task;
+        context = *p_context;
+        if (!context) {
+                context = new_context;
 
-                        if (task)
-                                set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
+                context->this = p_context;
+                context->task = task;
+                context->count = 0;
 
-                        if (!task || (task == current))
-                                wrmsrl(MSR_IA32_DS_AREA,
-                                       (unsigned long)context->ds);
-                }
+                if (task)
+                        set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
 
-                context->count++;
+                if (!task || (task == current))
+                        wrmsrl(MSR_IA32_DS_AREA, (unsigned long)context->ds);
 
-                spin_unlock_irqrestore(&ds_lock, irq);
-        } else {
-                spin_lock_irqsave(&ds_lock, irq);
+                *p_context = context;
+        }
 
-                context = *p_context;
-                if (context)
-                        context->count++;
+        context->count++;
 
-                spin_unlock_irqrestore(&ds_lock, irq);
+        spin_unlock_irqrestore(&ds_lock, irq);
 
-                if (!context)
-                        context = ds_get_context(task);
-        }
+        if (context != new_context)
+                kfree(new_context);
 
         return context;
 }