xref: /openbmc/linux/arch/x86/kernel/process.c (revision 22246614)
1 #include <linux/errno.h>
2 #include <linux/kernel.h>
3 #include <linux/mm.h>
4 #include <linux/smp.h>
5 #include <linux/slab.h>
6 #include <linux/sched.h>
7 #include <linux/module.h>
8 #include <linux/pm.h>
9 
10 struct kmem_cache *task_xstate_cachep;
11 
12 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
13 {
14 	*dst = *src;
15 	if (src->thread.xstate) {
16 		dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
17 						      GFP_KERNEL);
18 		if (!dst->thread.xstate)
19 			return -ENOMEM;
20 		WARN_ON((unsigned long)dst->thread.xstate & 15);
21 		memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
22 	}
23 	return 0;
24 }
25 
26 void free_thread_xstate(struct task_struct *tsk)
27 {
28 	if (tsk->thread.xstate) {
29 		kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
30 		tsk->thread.xstate = NULL;
31 	}
32 }
33 
34 void free_thread_info(struct thread_info *ti)
35 {
36 	free_thread_xstate(ti->task);
37 	free_pages((unsigned long)ti, get_order(THREAD_SIZE));
38 }
39 
40 void arch_task_cache_init(void)
41 {
42         task_xstate_cachep =
43         	kmem_cache_create("task_xstate", xstate_size,
44 				  __alignof__(union thread_xstate),
45 				  SLAB_PANIC, NULL);
46 }
47 
48 static void do_nothing(void *unused)
49 {
50 }
51 
52 /*
53  * cpu_idle_wait - Used to ensure that all the CPUs discard old value of
54  * pm_idle and update to new pm_idle value. Required while changing pm_idle
55  * handler on SMP systems.
56  *
57  * Caller must have changed pm_idle to the new value before the call. Old
58  * pm_idle value will not be used by any CPU after the return of this function.
59  */
60 void cpu_idle_wait(void)
61 {
62 	smp_mb();
63 	/* kick all the CPUs so that they exit out of pm_idle */
64 	smp_call_function(do_nothing, NULL, 0, 1);
65 }
66 EXPORT_SYMBOL_GPL(cpu_idle_wait);
67 
68 /*
69  * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
70  * which can obviate IPI to trigger checking of need_resched.
71  * We execute MONITOR against need_resched and enter optimized wait state
72  * through MWAIT. Whenever someone changes need_resched, we would be woken
73  * up from MWAIT (without an IPI).
74  *
75  * New with Core Duo processors, MWAIT can take some hints based on CPU
76  * capability.
77  */
78 void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
79 {
80 	if (!need_resched()) {
81 		__monitor((void *)&current_thread_info()->flags, 0, 0);
82 		smp_mb();
83 		if (!need_resched())
84 			__mwait(ax, cx);
85 	}
86 }
87 
88 /* Default MONITOR/MWAIT with no hints, used for default C1 state */
89 static void mwait_idle(void)
90 {
91 	if (!need_resched()) {
92 		__monitor((void *)&current_thread_info()->flags, 0, 0);
93 		smp_mb();
94 		if (!need_resched())
95 			__sti_mwait(0, 0);
96 		else
97 			local_irq_enable();
98 	} else
99 		local_irq_enable();
100 }
101 
102 
103 static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
104 {
105 	if (force_mwait)
106 		return 1;
107 	/* Any C1 states supported? */
108 	return c->cpuid_level >= 5 && ((cpuid_edx(5) >> 4) & 0xf) > 0;
109 }
110 
111 /*
112  * On SMP it's slightly faster (but much more power-consuming!)
113  * to poll the ->work.need_resched flag instead of waiting for the
114  * cross-CPU IPI to arrive. Use this option with caution.
115  */
116 static void poll_idle(void)
117 {
118 	local_irq_enable();
119 	cpu_relax();
120 }
121 
122 void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
123 {
124 	static int selected;
125 
126 	if (selected)
127 		return;
128 #ifdef CONFIG_X86_SMP
129 	if (pm_idle == poll_idle && smp_num_siblings > 1) {
130 		printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
131 			" performance may degrade.\n");
132 	}
133 #endif
134 	if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
135 		/*
136 		 * Skip, if setup has overridden idle.
137 		 * One CPU supports mwait => All CPUs supports mwait
138 		 */
139 		if (!pm_idle) {
140 			printk(KERN_INFO "using mwait in idle threads.\n");
141 			pm_idle = mwait_idle;
142 		}
143 	}
144 	selected = 1;
145 }
146 
147 static int __init idle_setup(char *str)
148 {
149 	if (!strcmp(str, "poll")) {
150 		printk("using polling idle threads.\n");
151 		pm_idle = poll_idle;
152 	} else if (!strcmp(str, "mwait"))
153 		force_mwait = 1;
154 	else
155 		return -1;
156 
157 	boot_option_idle_override = 1;
158 	return 0;
159 }
160 early_param("idle", idle_setup);
161 
162