From cc1dc6d039ced64c2f8b8457bf1cccf4ecfc5942 Mon Sep 17 00:00:00 2001 From: Markus Metzger Date: Tue, 16 Dec 2008 15:51:03 +0100 Subject: [PATCH] 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 Signed-off-by: Ingo Molnar --- arch/x86/kernel/ds.c | 58 +++++++++++++++++++------------------------- 1 file 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; } -- GitLab