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x86, bts: remove recursion from get_context

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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>
This commit is contained in:
Markus Metzger 2008-12-16 15:51:03 +01:00 committed by Ingo Molnar
parent 9dfc3bc7d2
commit cc1dc6d039
1 changed files with 28 additions and 36 deletions
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64
arch/x86/kernel/ds.c
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@ -232,54 +232,46 @@ static DEFINE_PER_CPU(struct ds_context *, system_context_array);
#define system_context per_cpu(system_context_array, smp_processor_id()) #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 = struct ds_context **p_context =
(task ? &task->thread.ds_ctx : &system_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; 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) { if (!context) {
context = kzalloc(sizeof(*context), GFP_KERNEL); context = new_context;
if (!context)
return NULL;
spin_lock_irqsave(&ds_lock, irq); context->this = p_context;
context->task = task;
context->count = 0;
if (*p_context) { if (task)
kfree(context); set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
context = *p_context; if (!task || (task == current))
} else { wrmsrl(MSR_IA32_DS_AREA, (unsigned long)context->ds);
*p_context = context;
context->this = p_context; *p_context = 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);
} }
context->count++;
spin_unlock_irqrestore(&ds_lock, irq);
if (context != new_context)
kfree(new_context);
return context; return context;
} }