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Commit cc1dc6d0 authored by Markus Metzger's avatar Markus Metzger Committed by Ingo Molnar
Browse files

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: default avatarMarkus Metzger <markus.t.metzger@intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9dfc3bc7

arch/x86/kernel/ds.c

+25 −33
Original line number Diff line number Diff line
@@ -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)

	/* 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);



		if (*p_context) {

			kfree(context);



	context = *p_context;

		} else {

			*p_context = context;

	if (!context) {

		context = new_context;



		context->this = p_context;

		context->task = task;

		context->count = 0;



		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++;

			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++;



	spin_unlock_irqrestore(&ds_lock, irq);



		if (!context)

			context = ds_get_context(task);

	}

	if (context != new_context)

		kfree(new_context);



	return context;

}