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>
diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index dc1e712..0dc7959 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -232,54 +232,46 @@
#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;
+ /* Chances are small that we already have a context. */
+ new_context = kzalloc(sizeof(*new_context), GFP_KERNEL);
+ if (!new_context)
+ return NULL;
+
+ spin_lock_irqsave(&ds_lock, irq);
+
+ context = *p_context;
if (!context) {
- context = kzalloc(sizeof(*context), GFP_KERNEL);
- if (!context)
- return NULL;
+ context = new_context;
- spin_lock_irqsave(&ds_lock, irq);
+ context->this = p_context;
+ context->task = task;
+ context->count = 0;
- if (*p_context) {
- kfree(context);
+ if (task)
+ set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
- context = *p_context;
- } else {
- *p_context = context;
+ if (!task || (task == current))
+ wrmsrl(MSR_IA32_DS_AREA, (unsigned long)context->ds);
- context->this = p_context;
- context->task = task;
-
- if (task)
- set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
-
- if (!task || (task == current))
- wrmsrl(MSR_IA32_DS_AREA,
- (unsigned long)context->ds);
- }
-
- context->count++;
-
- spin_unlock_irqrestore(&ds_lock, irq);
- } else {
- spin_lock_irqsave(&ds_lock, irq);
-
- context = *p_context;
- if (context)
- context->count++;
-
- spin_unlock_irqrestore(&ds_lock, irq);
-
- if (!context)
- context = ds_get_context(task);
+ *p_context = context;
}
+ context->count++;
+
+ spin_unlock_irqrestore(&ds_lock, irq);
+
+ if (context != new_context)
+ kfree(new_context);
+
return context;
}