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 static int force_mwait __cpuinitdata;
  19
  20 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
  21 {
  22         *dst = *src;
  23         if (src->thread.xstate) {
  24                 dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
  25                                                       GFP_KERNEL);
  26                 if (!dst->thread.xstate)
  27                         return -ENOMEM;
  28                 WARN_ON((unsigned long)dst->thread.xstate & 15);
  29                 memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
  30         }
  31         return 0;
  32 }
  33
  34 void free_thread_xstate(struct task_struct *tsk)
  35 {
  36         if (tsk->thread.xstate) {
  37                 kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
  38                 tsk->thread.xstate = NULL;
  39         }
  40 }
  41
  42 void free_thread_info(struct thread_info *ti)
  43 {
  44         free_thread_xstate(ti->task);
  45         free_pages((unsigned long)ti, get_order(THREAD_SIZE));
  46 }
  47
  48 void arch_task_cache_init(void)
  49 {
  50         task_xstate_cachep =
  51                 kmem_cache_create("task_xstate", xstate_size,
  52                                   __alignof__(union thread_xstate),
  53                                   SLAB_PANIC, NULL);
  54 }
  55
  56 /*
  57  * Idle related variables and functions
  58  */
  59 unsigned long boot_option_idle_override = 0;
  60 EXPORT_SYMBOL(boot_option_idle_override);
  61
  62 /*
  63  * Powermanagement idle function, if any..
  64  */
  65 void (*pm_idle)(void);
  66 EXPORT_SYMBOL(pm_idle);
  67
  68 #ifdef CONFIG_X86_32
  69 /*
  70  * This halt magic was a workaround for ancient floppy DMA
  71  * wreckage. It should be safe to remove.
  72  */
  73 static int hlt_counter;
  74 void disable_hlt(void)
  75 {
  76         hlt_counter++;
  77 }
  78 EXPORT_SYMBOL(disable_hlt);
  79
  80 void enable_hlt(void)
  81 {
  82         hlt_counter--;
  83 }
  84 EXPORT_SYMBOL(enable_hlt);
  85
  86 static inline int hlt_use_halt(void)
  87 {
  88         return (!hlt_counter && boot_cpu_data.hlt_works_ok);
  89 }
  90 #else
  91 static inline int hlt_use_halt(void)
  92 {
  93         return 1;
  94 }
  95 #endif
  96
  97 /*
  98  * We use this if we don't have any better
  99  * idle routine..
 100  */
 101 void default_idle(void)
 102 {
 103         if (hlt_use_halt()) {
 104                 current_thread_info()->status &= ~TS_POLLING;
 105                 /*
 106                  * TS_POLLING-cleared state must be visible before we
 107                  * test NEED_RESCHED:
 108                  */
 109                 smp_mb();
 110
 111                 if (!need_resched())
 112                         safe_halt();    /* enables interrupts racelessly */
 113                 else
 114                         local_irq_enable();
 115                 current_thread_info()->status |= TS_POLLING;
 116         } else {
 117                 local_irq_enable();
 118                 /* loop is done by the caller */
 119                 cpu_relax();
 120         }
 121 }
 122 #ifdef CONFIG_APM_MODULE
 123 EXPORT_SYMBOL(default_idle);
 124 #endif
 125
 126 static void do_nothing(void *unused)
 127 {
 128 }
 129
 130 /*
 131  * cpu_idle_wait - Used to ensure that all the CPUs discard old value of
 132  * pm_idle and update to new pm_idle value. Required while changing pm_idle
 133  * handler on SMP systems.
 134  *
 135  * Caller must have changed pm_idle to the new value before the call. Old
 136  * pm_idle value will not be used by any CPU after the return of this function.
 137  */
 138 void cpu_idle_wait(void)
 139 {
 140         smp_mb();
 141         /* kick all the CPUs so that they exit out of pm_idle */
 142         smp_call_function(do_nothing, NULL, 1);
 143 }
 144 EXPORT_SYMBOL_GPL(cpu_idle_wait);
 145
 146 /*
 147  * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
 148  * which can obviate IPI to trigger checking of need_resched.
 149  * We execute MONITOR against need_resched and enter optimized wait state
 150  * through MWAIT. Whenever someone changes need_resched, we would be woken
 151  * up from MWAIT (without an IPI).
 152  *
 153  * New with Core Duo processors, MWAIT can take some hints based on CPU
 154  * capability.
 155  */
 156 void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
 157 {
 158         if (!need_resched()) {
 159                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 160                 smp_mb();
 161                 if (!need_resched())
 162                         __mwait(ax, cx);
 163         }
 164 }
 165
 166 /* Default MONITOR/MWAIT with no hints, used for default C1 state */
 167 static void mwait_idle(void)
 168 {
 169         if (!need_resched()) {
 170                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 171                 smp_mb();
 172                 if (!need_resched())
 173                         __sti_mwait(0, 0);
 174                 else
 175                         local_irq_enable();
 176         } else
 177                 local_irq_enable();
 178 }
 179
 180 /*
 181  * On SMP it's slightly faster (but much more power-consuming!)
 182  * to poll the ->work.need_resched flag instead of waiting for the
 183  * cross-CPU IPI to arrive. Use this option with caution.
 184  */
 185 static void poll_idle(void)
 186 {
 187         local_irq_enable();
 188         while (!need_resched())
 189                 cpu_relax();
 190 }
 191
 192 /*
 193  * mwait selection logic:
 194  *
 195  * It depends on the CPU. For AMD CPUs that support MWAIT this is
 196  * wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings
 197  * then depend on a clock divisor and current Pstate of the core. If
 198  * all cores of a processor are in halt state (C1) the processor can
 199  * enter the C1E (C1 enhanced) state. If mwait is used this will never
 200  * happen.
 201  *
 202  * idle=mwait overrides this decision and forces the usage of mwait.
 203  */
 204 static int __cpuinitdata force_mwait;
 205
 206 #define MWAIT_INFO                      0x05
 207 #define MWAIT_ECX_EXTENDED_INFO         0x01
 208 #define MWAIT_EDX_C1                    0xf0
 209
 210 static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
 211 {
 212         u32 eax, ebx, ecx, edx;
 213
 214         if (force_mwait)
 215                 return 1;
 216
 217         if (c->cpuid_level < MWAIT_INFO)
 218                 return 0;
 219
 220         cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
 221         /* Check, whether EDX has extended info about MWAIT */
 222         if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
 223                 return 1;
 224
 225         /*
 226          * edx enumeratios MONITOR/MWAIT extensions. Check, whether
 227          * C1  supports MWAIT
 228          */
 229         return (edx & MWAIT_EDX_C1);
 230 }
 231
 232 /*
 233  * Check for AMD CPUs, which have potentially C1E support
 234  */
 235 static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
 236 {
 237         if (c->x86_vendor != X86_VENDOR_AMD)
 238                 return 0;
 239
 240         if (c->x86 < 0x0F)
 241                 return 0;
 242
 243         /* Family 0x0f models < rev F do not have C1E */
 244         if (c->x86 == 0x0f && c->x86_model < 0x40)
 245                 return 0;
 246
 247         return 1;
 248 }
 249
 250 /*
 251  * C1E aware idle routine. We check for C1E active in the interrupt
 252  * pending message MSR. If we detect C1E, then we handle it the same
 253  * way as C3 power states (local apic timer and TSC stop)
 254  */
 255 static void c1e_idle(void)
 256 {
 257         static cpumask_t c1e_mask = CPU_MASK_NONE;
 258         static int c1e_detected;
 259
 260         if (need_resched())
 261                 return;
 262
 263         if (!c1e_detected) {
 264                 u32 lo, hi;
 265
 266                 rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
 267                 if (lo & K8_INTP_C1E_ACTIVE_MASK) {
 268                         c1e_detected = 1;
 269                         mark_tsc_unstable("TSC halt in C1E");
 270                         printk(KERN_INFO "System has C1E enabled\n");
 271                 }
 272         }
 273
 274         if (c1e_detected) {
 275                 int cpu = smp_processor_id();
 276
 277                 if (!cpu_isset(cpu, c1e_mask)) {
 278                         cpu_set(cpu, c1e_mask);
 279                         /*
 280                          * Force broadcast so ACPI can not interfere. Needs
 281                          * to run with interrupts enabled as it uses
 282                          * smp_function_call.
 283                          */
 284                         local_irq_enable();
 285                         clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_FORCE,
 286                                            &cpu);
 287                         printk(KERN_INFO "Switch to broadcast mode on CPU%d\n",
 288                                cpu);
 289                         local_irq_disable();
 290                 }
 291                 clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
 292
 293                 default_idle();
 294
 295                 /*
 296                  * The switch back from broadcast mode needs to be
 297                  * called with interrupts disabled.
 298                  */
 299                  local_irq_disable();
 300                  clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
 301                  local_irq_enable();
 302         } else
 303                 default_idle();
 304 }
 305
 306 void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 307 {
 308 #ifdef CONFIG_X86_SMP
 309         if (pm_idle == poll_idle && smp_num_siblings > 1) {
 310                 printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
 311                         " performance may degrade.\n");
 312         }
 313 #endif
 314         if (pm_idle)
 315                 return;
 316
 317         if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
 318                 /*
 319                  * One CPU supports mwait => All CPUs supports mwait
 320                  */
 321                 printk(KERN_INFO "using mwait in idle threads.\n");
 322                 pm_idle = mwait_idle;
 323         } else if (check_c1e_idle(c)) {
 324                 printk(KERN_INFO "using C1E aware idle routine\n");
 325                 pm_idle = c1e_idle;
 326         } else
 327                 pm_idle = default_idle;
 328 }
 329
 330 static int __init idle_setup(char *str)
 331 {
 332         if (!str)
 333                 return -EINVAL;
 334
 335         if (!strcmp(str, "poll")) {
 336                 printk("using polling idle threads.\n");
 337                 pm_idle = poll_idle;
 338         } else if (!strcmp(str, "mwait"))
 339                 force_mwait = 1;
 340         else if (!strcmp(str, "halt")) {
 341                 /*
 342                  * When the boot option of idle=halt is added, halt is
 343                  * forced to be used for CPU idle. In such case CPU C2/C3
 344                  * won't be used again.
 345                  * To continue to load the CPU idle driver, don't touch
 346                  * the boot_option_idle_override.
 347                  */
 348                 pm_idle = default_idle;
 349                 idle_halt = 1;
 350                 return 0;
 351         } else if (!strcmp(str, "nomwait")) {
 352                 /*
 353                  * If the boot option of "idle=nomwait" is added,
 354                  * it means that mwait will be disabled for CPU C2/C3
 355                  * states. In such case it won't touch the variable
 356                  * of boot_option_idle_override.
 357                  */
 358                 idle_nomwait = 1;
 359                 return 0;
 360         } else
 361                 return -1;
 362
 363         boot_option_idle_override = 1;
 364         return 0;
 365 }
 366 early_param("idle", idle_setup);
 367