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 *)¤t_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 *)¤t_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