arch/x86/kernel/process.c

   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 #include <linux/clockchips.h>
  10 #include <asm/system.h>
  11
  12 unsigned long idle_halt;
  13 EXPORT_SYMBOL(idle_halt);
  14 unsigned long idle_nomwait;
  15 EXPORT_SYMBOL(idle_nomwait);
  16
  17 struct kmem_cache *task_xstate_cachep;
  18
  19 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
  20 {
  21         *dst = *src;
  22         if (src->thread.xstate) {
  23                 dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
  24                                                       GFP_KERNEL);
  25                 if (!dst->thread.xstate)
  26                         return -ENOMEM;
  27                 WARN_ON((unsigned long)dst->thread.xstate & 15);
  28                 memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
  29         }
  30         return 0;
  31 }
  32
  33 void free_thread_xstate(struct task_struct *tsk)
  34 {
  35         if (tsk->thread.xstate) {
  36                 kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
  37                 tsk->thread.xstate = NULL;
  38         }
  39 }
  40
  41 void free_thread_info(struct thread_info *ti)
  42 {
  43         free_thread_xstate(ti->task);
  44         free_pages((unsigned long)ti, get_order(THREAD_SIZE));
  45 }
  46
  47 void arch_task_cache_init(void)
  48 {
  49         task_xstate_cachep =
  50                 kmem_cache_create("task_xstate", xstate_size,
  51                                   __alignof__(union thread_xstate),
  52                                   SLAB_PANIC, NULL);
  53 }
  54
  55 /*
  56  * Idle related variables and functions
  57  */
  58 unsigned long boot_option_idle_override = 0;
  59 EXPORT_SYMBOL(boot_option_idle_override);
  60
  61 /*
  62  * Powermanagement idle function, if any..
  63  */
  64 void (*pm_idle)(void);
  65 EXPORT_SYMBOL(pm_idle);
  66
  67 #ifdef CONFIG_X86_32
  68 /*
  69  * This halt magic was a workaround for ancient floppy DMA
  70  * wreckage. It should be safe to remove.
  71  */
  72 static int hlt_counter;
  73 void disable_hlt(void)
  74 {
  75         hlt_counter++;
  76 }
  77 EXPORT_SYMBOL(disable_hlt);
  78
  79 void enable_hlt(void)
  80 {
  81         hlt_counter--;
  82 }
  83 EXPORT_SYMBOL(enable_hlt);
  84
  85 static inline int hlt_use_halt(void)
  86 {
  87         return (!hlt_counter && boot_cpu_data.hlt_works_ok);
  88 }
  89 #else
  90 static inline int hlt_use_halt(void)
  91 {
  92         return 1;
  93 }
  94 #endif
  95
  96 /*
  97  * We use this if we don't have any better
  98  * idle routine..
  99  */
 100 void default_idle(void)
 101 {
 102         if (hlt_use_halt()) {
 103                 current_thread_info()->status &= ~TS_POLLING;
 104                 /*
 105                  * TS_POLLING-cleared state must be visible before we
 106                  * test NEED_RESCHED:
 107                  */
 108                 smp_mb();
 109
 110                 if (!need_resched())
 111                         safe_halt();    /* enables interrupts racelessly */
 112                 else
 113                         local_irq_enable();
 114                 current_thread_info()->status |= TS_POLLING;
 115         } else {
 116                 local_irq_enable();
 117                 /* loop is done by the caller */
 118                 cpu_relax();
 119         }
 120 }
 121 #ifdef CONFIG_APM_MODULE
 122 EXPORT_SYMBOL(default_idle);
 123 #endif
 124
 125 static void do_nothing(void *unused)
 126 {
 127 }
 128
 129 /*
 130  * cpu_idle_wait - Used to ensure that all the CPUs discard old value of
 131  * pm_idle and update to new pm_idle value. Required while changing pm_idle
 132  * handler on SMP systems.
 133  *
 134  * Caller must have changed pm_idle to the new value before the call. Old
 135  * pm_idle value will not be used by any CPU after the return of this function.
 136  */
 137 void cpu_idle_wait(void)
 138 {
 139         smp_mb();
 140         /* kick all the CPUs so that they exit out of pm_idle */
 141         smp_call_function(do_nothing, NULL, 1);
 142 }
 143 EXPORT_SYMBOL_GPL(cpu_idle_wait);
 144
 145 /*
 146  * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
 147  * which can obviate IPI to trigger checking of need_resched.
 148  * We execute MONITOR against need_resched and enter optimized wait state
 149  * through MWAIT. Whenever someone changes need_resched, we would be woken
 150  * up from MWAIT (without an IPI).
 151  *
 152  * New with Core Duo processors, MWAIT can take some hints based on CPU
 153  * capability.
 154  */
 155 void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
 156 {
 157         if (!need_resched()) {
 158                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 159                 smp_mb();
 160                 if (!need_resched())
 161                         __mwait(ax, cx);
 162         }
 163 }
 164
 165 /* Default MONITOR/MWAIT with no hints, used for default C1 state */
 166 static void mwait_idle(void)
 167 {
 168         if (!need_resched()) {
 169                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 170                 smp_mb();
 171                 if (!need_resched())
 172                         __sti_mwait(0, 0);
 173                 else
 174                         local_irq_enable();
 175         } else
 176                 local_irq_enable();
 177 }
 178
 179 /*
 180  * On SMP it's slightly faster (but much more power-consuming!)
 181  * to poll the ->work.need_resched flag instead of waiting for the
 182  * cross-CPU IPI to arrive. Use this option with caution.
 183  */
 184 static void poll_idle(void)
 185 {
 186         local_irq_enable();
 187         cpu_relax();
 188 }
 189
 190 /*
 191  * mwait selection logic:
 192  *
 193  * It depends on the CPU. For AMD CPUs that support MWAIT this is
 194  * wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings
 195  * then depend on a clock divisor and current Pstate of the core. If
 196  * all cores of a processor are in halt state (C1) the processor can
 197  * enter the C1E (C1 enhanced) state. If mwait is used this will never
 198  * happen.
 199  *
 200  * idle=mwait overrides this decision and forces the usage of mwait.
 201  */
 202
 203 #define MWAIT_INFO                      0x05
 204 #define MWAIT_ECX_EXTENDED_INFO         0x01
 205 #define MWAIT_EDX_C1                    0xf0
 206
 207 static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
 208 {
 209         u32 eax, ebx, ecx, edx;
 210
 211         if (force_mwait)
 212                 return 1;
 213
 214         if (c->cpuid_level < MWAIT_INFO)
 215                 return 0;
 216
 217         cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
 218         /* Check, whether EDX has extended info about MWAIT */
 219         if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
 220                 return 1;
 221
 222         /*
 223          * edx enumeratios MONITOR/MWAIT extensions. Check, whether
 224          * C1  supports MWAIT
 225          */
 226         return (edx & MWAIT_EDX_C1);
 227 }
 228
 229 /*
 230  * Check for AMD CPUs, which have potentially C1E support
 231  */
 232 static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
 233 {
 234         if (c->x86_vendor != X86_VENDOR_AMD)
 235                 return 0;
 236
 237         if (c->x86 < 0x0F)
 238                 return 0;
 239
 240         /* Family 0x0f models < rev F do not have C1E */
 241         if (c->x86 == 0x0f && c->x86_model < 0x40)
 242                 return 0;
 243
 244         return 1;
 245 }
 246
 247 /*
 248  * C1E aware idle routine. We check for C1E active in the interrupt
 249  * pending message MSR. If we detect C1E, then we handle it the same
 250  * way as C3 power states (local apic timer and TSC stop)
 251  */
 252 static void c1e_idle(void)
 253 {
 254         static cpumask_t c1e_mask = CPU_MASK_NONE;
 255         static int c1e_detected;
 256
 257         if (need_resched())
 258                 return;
 259
 260         if (!c1e_detected) {
 261                 u32 lo, hi;
 262
 263                 rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
 264                 if (lo & K8_INTP_C1E_ACTIVE_MASK) {
 265                         c1e_detected = 1;
 266                         mark_tsc_unstable("TSC halt in C1E");
 267                         printk(KERN_INFO "System has C1E enabled\n");
 268                 }
 269         }
 270
 271         if (c1e_detected) {
 272                 int cpu = smp_processor_id();
 273
 274                 if (!cpu_isset(cpu, c1e_mask)) {
 275                         cpu_set(cpu, c1e_mask);
 276                         /*
 277                          * Force broadcast so ACPI can not interfere. Needs
 278                          * to run with interrupts enabled as it uses
 279                          * smp_function_call.
 280                          */
 281                         local_irq_enable();
 282                         clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_FORCE,
 283                                            &cpu);
 284                         printk(KERN_INFO "Switch to broadcast mode on CPU%d\n",
 285                                cpu);
 286                         local_irq_disable();
 287                 }
 288                 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
 289
 290                 default_idle();
 291
 292                 /*
 293                  * The switch back from broadcast mode needs to be
 294                  * called with interrupts disabled.
 295                  */
 296                  local_irq_disable();
 297                  clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
 298                  local_irq_enable();
 299         } else
 300                 default_idle();
 301 }
 302
 303 void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 304 {
 305 #ifdef CONFIG_X86_SMP
 306         if (pm_idle == poll_idle && smp_num_siblings > 1) {
 307                 printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
 308                         " performance may degrade.\n");
 309         }
 310 #endif
 311         if (pm_idle)
 312                 return;
 313
 314         if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
 315                 /*
 316                  * One CPU supports mwait => All CPUs supports mwait
 317                  */
 318                 printk(KERN_INFO "using mwait in idle threads.\n");
 319                 pm_idle = mwait_idle;
 320         } else if (check_c1e_idle(c)) {
 321                 printk(KERN_INFO "using C1E aware idle routine\n");
 322                 pm_idle = c1e_idle;
 323         } else
 324                 pm_idle = default_idle;
 325 }
 326
 327 static int __init idle_setup(char *str)
 328 {
 329         if (!strcmp(str, "poll")) {
 330                 printk("using polling idle threads.\n");
 331                 pm_idle = poll_idle;
 332         } else if (!strcmp(str, "mwait"))
 333                 force_mwait = 1;
 334         else if (!strcmp(str, "halt")) {
 335                 /*
 336                  * When the boot option of idle=halt is added, halt is
 337                  * forced to be used for CPU idle. In such case CPU C2/C3
 338                  * won't be used again.
 339                  * To continue to load the CPU idle driver, don't touch
 340                  * the boot_option_idle_override.
 341                  */
 342                 pm_idle = default_idle;
 343                 idle_halt = 1;
 344                 return 0;
 345         } else if (!strcmp(str, "nomwait")) {
 346                 /*
 347                  * If the boot option of "idle=nomwait" is added,
 348                  * it means that mwait will be disabled for CPU C2/C3
 349                  * states. In such case it won't touch the variable
 350                  * of boot_option_idle_override.
 351                  */
 352                 idle_nomwait = 1;
 353                 return 0;
 354         } else
 355                 return -1;
 356
 357         boot_option_idle_override = 1;
 358         return 0;
 359 }
 360 early_param("idle", idle_setup);
 361