linux/arch/x86/kernel/process.c
Thomas Gleixner 250981e6e1 x86: reduce preemption off section in exit thread
Impact: latency improvement

No need to keep preemption disabled over the kfree call.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-03-16 15:32:28 +01:00

603 lines
14 KiB
C

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/prctl.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/pm.h>
#include <linux/clockchips.h>
#include <linux/ftrace.h>
#include <asm/system.h>
#include <asm/apic.h>
#include <asm/idle.h>
#include <asm/uaccess.h>
#include <asm/i387.h>
unsigned long idle_halt;
EXPORT_SYMBOL(idle_halt);
unsigned long idle_nomwait;
EXPORT_SYMBOL(idle_nomwait);
struct kmem_cache *task_xstate_cachep;
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
*dst = *src;
if (src->thread.xstate) {
dst->thread.xstate = kmem_cache_alloc(task_xstate_cachep,
GFP_KERNEL);
if (!dst->thread.xstate)
return -ENOMEM;
WARN_ON((unsigned long)dst->thread.xstate & 15);
memcpy(dst->thread.xstate, src->thread.xstate, xstate_size);
}
return 0;
}
void free_thread_xstate(struct task_struct *tsk)
{
if (tsk->thread.xstate) {
kmem_cache_free(task_xstate_cachep, tsk->thread.xstate);
tsk->thread.xstate = NULL;
}
}
void free_thread_info(struct thread_info *ti)
{
free_thread_xstate(ti->task);
free_pages((unsigned long)ti, get_order(THREAD_SIZE));
}
void arch_task_cache_init(void)
{
task_xstate_cachep =
kmem_cache_create("task_xstate", xstate_size,
__alignof__(union thread_xstate),
SLAB_PANIC, NULL);
}
/*
* Free current thread data structures etc..
*/
void exit_thread(void)
{
struct task_struct *me = current;
struct thread_struct *t = &me->thread;
unsigned long *bp = t->io_bitmap_ptr;
if (bp) {
struct tss_struct *tss = &per_cpu(init_tss, get_cpu());
t->io_bitmap_ptr = NULL;
clear_thread_flag(TIF_IO_BITMAP);
/*
* Careful, clear this in the TSS too:
*/
memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
t->io_bitmap_max = 0;
put_cpu();
kfree(bp);
}
ds_exit_thread(current);
}
void flush_thread(void)
{
struct task_struct *tsk = current;
#ifdef CONFIG_X86_64
if (test_tsk_thread_flag(tsk, TIF_ABI_PENDING)) {
clear_tsk_thread_flag(tsk, TIF_ABI_PENDING);
if (test_tsk_thread_flag(tsk, TIF_IA32)) {
clear_tsk_thread_flag(tsk, TIF_IA32);
} else {
set_tsk_thread_flag(tsk, TIF_IA32);
current_thread_info()->status |= TS_COMPAT;
}
}
#endif
clear_tsk_thread_flag(tsk, TIF_DEBUG);
tsk->thread.debugreg0 = 0;
tsk->thread.debugreg1 = 0;
tsk->thread.debugreg2 = 0;
tsk->thread.debugreg3 = 0;
tsk->thread.debugreg6 = 0;
tsk->thread.debugreg7 = 0;
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
/*
* Forget coprocessor state..
*/
tsk->fpu_counter = 0;
clear_fpu(tsk);
clear_used_math();
}
static void hard_disable_TSC(void)
{
write_cr4(read_cr4() | X86_CR4_TSD);
}
void disable_TSC(void)
{
preempt_disable();
if (!test_and_set_thread_flag(TIF_NOTSC))
/*
* Must flip the CPU state synchronously with
* TIF_NOTSC in the current running context.
*/
hard_disable_TSC();
preempt_enable();
}
static void hard_enable_TSC(void)
{
write_cr4(read_cr4() & ~X86_CR4_TSD);
}
static void enable_TSC(void)
{
preempt_disable();
if (test_and_clear_thread_flag(TIF_NOTSC))
/*
* Must flip the CPU state synchronously with
* TIF_NOTSC in the current running context.
*/
hard_enable_TSC();
preempt_enable();
}
int get_tsc_mode(unsigned long adr)
{
unsigned int val;
if (test_thread_flag(TIF_NOTSC))
val = PR_TSC_SIGSEGV;
else
val = PR_TSC_ENABLE;
return put_user(val, (unsigned int __user *)adr);
}
int set_tsc_mode(unsigned int val)
{
if (val == PR_TSC_SIGSEGV)
disable_TSC();
else if (val == PR_TSC_ENABLE)
enable_TSC();
else
return -EINVAL;
return 0;
}
void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
struct tss_struct *tss)
{
struct thread_struct *prev, *next;
prev = &prev_p->thread;
next = &next_p->thread;
if (test_tsk_thread_flag(next_p, TIF_DS_AREA_MSR) ||
test_tsk_thread_flag(prev_p, TIF_DS_AREA_MSR))
ds_switch_to(prev_p, next_p);
else if (next->debugctlmsr != prev->debugctlmsr)
update_debugctlmsr(next->debugctlmsr);
if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
set_debugreg(next->debugreg0, 0);
set_debugreg(next->debugreg1, 1);
set_debugreg(next->debugreg2, 2);
set_debugreg(next->debugreg3, 3);
/* no 4 and 5 */
set_debugreg(next->debugreg6, 6);
set_debugreg(next->debugreg7, 7);
}
if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
test_tsk_thread_flag(next_p, TIF_NOTSC)) {
/* prev and next are different */
if (test_tsk_thread_flag(next_p, TIF_NOTSC))
hard_disable_TSC();
else
hard_enable_TSC();
}
if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
/*
* Copy the relevant range of the IO bitmap.
* Normally this is 128 bytes or less:
*/
memcpy(tss->io_bitmap, next->io_bitmap_ptr,
max(prev->io_bitmap_max, next->io_bitmap_max));
} else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
/*
* Clear any possible leftover bits:
*/
memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
}
}
int sys_fork(struct pt_regs *regs)
{
return do_fork(SIGCHLD, regs->sp, regs, 0, NULL, NULL);
}
/*
* This is trivial, and on the face of it looks like it
* could equally well be done in user mode.
*
* Not so, for quite unobvious reasons - register pressure.
* In user mode vfork() cannot have a stack frame, and if
* done by calling the "clone()" system call directly, you
* do not have enough call-clobbered registers to hold all
* the information you need.
*/
int sys_vfork(struct pt_regs *regs)
{
return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->sp, regs, 0,
NULL, NULL);
}
/*
* Idle related variables and functions
*/
unsigned long boot_option_idle_override = 0;
EXPORT_SYMBOL(boot_option_idle_override);
/*
* Powermanagement idle function, if any..
*/
void (*pm_idle)(void);
EXPORT_SYMBOL(pm_idle);
#ifdef CONFIG_X86_32
/*
* This halt magic was a workaround for ancient floppy DMA
* wreckage. It should be safe to remove.
*/
static int hlt_counter;
void disable_hlt(void)
{
hlt_counter++;
}
EXPORT_SYMBOL(disable_hlt);
void enable_hlt(void)
{
hlt_counter--;
}
EXPORT_SYMBOL(enable_hlt);
static inline int hlt_use_halt(void)
{
return (!hlt_counter && boot_cpu_data.hlt_works_ok);
}
#else
static inline int hlt_use_halt(void)
{
return 1;
}
#endif
/*
* We use this if we don't have any better
* idle routine..
*/
void default_idle(void)
{
if (hlt_use_halt()) {
struct power_trace it;
trace_power_start(&it, POWER_CSTATE, 1);
current_thread_info()->status &= ~TS_POLLING;
/*
* TS_POLLING-cleared state must be visible before we
* test NEED_RESCHED:
*/
smp_mb();
if (!need_resched())
safe_halt(); /* enables interrupts racelessly */
else
local_irq_enable();
current_thread_info()->status |= TS_POLLING;
trace_power_end(&it);
} else {
local_irq_enable();
/* loop is done by the caller */
cpu_relax();
}
}
#ifdef CONFIG_APM_MODULE
EXPORT_SYMBOL(default_idle);
#endif
void stop_this_cpu(void *dummy)
{
local_irq_disable();
/*
* Remove this CPU:
*/
cpu_clear(smp_processor_id(), cpu_online_map);
disable_local_APIC();
for (;;) {
if (hlt_works(smp_processor_id()))
halt();
}
}
static void do_nothing(void *unused)
{
}
/*
* cpu_idle_wait - Used to ensure that all the CPUs discard old value of
* pm_idle and update to new pm_idle value. Required while changing pm_idle
* handler on SMP systems.
*
* Caller must have changed pm_idle to the new value before the call. Old
* pm_idle value will not be used by any CPU after the return of this function.
*/
void cpu_idle_wait(void)
{
smp_mb();
/* kick all the CPUs so that they exit out of pm_idle */
smp_call_function(do_nothing, NULL, 1);
}
EXPORT_SYMBOL_GPL(cpu_idle_wait);
/*
* This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
* which can obviate IPI to trigger checking of need_resched.
* We execute MONITOR against need_resched and enter optimized wait state
* through MWAIT. Whenever someone changes need_resched, we would be woken
* up from MWAIT (without an IPI).
*
* New with Core Duo processors, MWAIT can take some hints based on CPU
* capability.
*/
void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
{
struct power_trace it;
trace_power_start(&it, POWER_CSTATE, (ax>>4)+1);
if (!need_resched()) {
if (cpu_has(&current_cpu_data, X86_FEATURE_CLFLUSH_MONITOR))
clflush((void *)&current_thread_info()->flags);
__monitor((void *)&current_thread_info()->flags, 0, 0);
smp_mb();
if (!need_resched())
__mwait(ax, cx);
}
trace_power_end(&it);
}
/* Default MONITOR/MWAIT with no hints, used for default C1 state */
static void mwait_idle(void)
{
struct power_trace it;
if (!need_resched()) {
trace_power_start(&it, POWER_CSTATE, 1);
if (cpu_has(&current_cpu_data, X86_FEATURE_CLFLUSH_MONITOR))
clflush((void *)&current_thread_info()->flags);
__monitor((void *)&current_thread_info()->flags, 0, 0);
smp_mb();
if (!need_resched())
__sti_mwait(0, 0);
else
local_irq_enable();
trace_power_end(&it);
} else
local_irq_enable();
}
/*
* On SMP it's slightly faster (but much more power-consuming!)
* to poll the ->work.need_resched flag instead of waiting for the
* cross-CPU IPI to arrive. Use this option with caution.
*/
static void poll_idle(void)
{
struct power_trace it;
trace_power_start(&it, POWER_CSTATE, 0);
local_irq_enable();
while (!need_resched())
cpu_relax();
trace_power_end(&it);
}
/*
* mwait selection logic:
*
* It depends on the CPU. For AMD CPUs that support MWAIT this is
* wrong. Family 0x10 and 0x11 CPUs will enter C1 on HLT. Powersavings
* then depend on a clock divisor and current Pstate of the core. If
* all cores of a processor are in halt state (C1) the processor can
* enter the C1E (C1 enhanced) state. If mwait is used this will never
* happen.
*
* idle=mwait overrides this decision and forces the usage of mwait.
*/
static int __cpuinitdata force_mwait;
#define MWAIT_INFO 0x05
#define MWAIT_ECX_EXTENDED_INFO 0x01
#define MWAIT_EDX_C1 0xf0
static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
{
u32 eax, ebx, ecx, edx;
if (force_mwait)
return 1;
if (c->cpuid_level < MWAIT_INFO)
return 0;
cpuid(MWAIT_INFO, &eax, &ebx, &ecx, &edx);
/* Check, whether EDX has extended info about MWAIT */
if (!(ecx & MWAIT_ECX_EXTENDED_INFO))
return 1;
/*
* edx enumeratios MONITOR/MWAIT extensions. Check, whether
* C1 supports MWAIT
*/
return (edx & MWAIT_EDX_C1);
}
/*
* Check for AMD CPUs, which have potentially C1E support
*/
static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
{
if (c->x86_vendor != X86_VENDOR_AMD)
return 0;
if (c->x86 < 0x0F)
return 0;
/* Family 0x0f models < rev F do not have C1E */
if (c->x86 == 0x0f && c->x86_model < 0x40)
return 0;
return 1;
}
static cpumask_t c1e_mask = CPU_MASK_NONE;
static int c1e_detected;
void c1e_remove_cpu(int cpu)
{
cpu_clear(cpu, c1e_mask);
}
/*
* C1E aware idle routine. We check for C1E active in the interrupt
* pending message MSR. If we detect C1E, then we handle it the same
* way as C3 power states (local apic timer and TSC stop)
*/
static void c1e_idle(void)
{
if (need_resched())
return;
if (!c1e_detected) {
u32 lo, hi;
rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
if (lo & K8_INTP_C1E_ACTIVE_MASK) {
c1e_detected = 1;
if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
mark_tsc_unstable("TSC halt in AMD C1E");
printk(KERN_INFO "System has AMD C1E enabled\n");
set_cpu_cap(&boot_cpu_data, X86_FEATURE_AMDC1E);
}
}
if (c1e_detected) {
int cpu = smp_processor_id();
if (!cpu_isset(cpu, c1e_mask)) {
cpu_set(cpu, c1e_mask);
/*
* Force broadcast so ACPI can not interfere. Needs
* to run with interrupts enabled as it uses
* smp_function_call.
*/
local_irq_enable();
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_FORCE,
&cpu);
printk(KERN_INFO "Switch to broadcast mode on CPU%d\n",
cpu);
local_irq_disable();
}
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
default_idle();
/*
* The switch back from broadcast mode needs to be
* called with interrupts disabled.
*/
local_irq_disable();
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
local_irq_enable();
} else
default_idle();
}
void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
{
#ifdef CONFIG_SMP
if (pm_idle == poll_idle && smp_num_siblings > 1) {
printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
" performance may degrade.\n");
}
#endif
if (pm_idle)
return;
if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
/*
* One CPU supports mwait => All CPUs supports mwait
*/
printk(KERN_INFO "using mwait in idle threads.\n");
pm_idle = mwait_idle;
} else if (check_c1e_idle(c)) {
printk(KERN_INFO "using C1E aware idle routine\n");
pm_idle = c1e_idle;
} else
pm_idle = default_idle;
}
static int __init idle_setup(char *str)
{
if (!str)
return -EINVAL;
if (!strcmp(str, "poll")) {
printk("using polling idle threads.\n");
pm_idle = poll_idle;
} else if (!strcmp(str, "mwait"))
force_mwait = 1;
else if (!strcmp(str, "halt")) {
/*
* When the boot option of idle=halt is added, halt is
* forced to be used for CPU idle. In such case CPU C2/C3
* won't be used again.
* To continue to load the CPU idle driver, don't touch
* the boot_option_idle_override.
*/
pm_idle = default_idle;
idle_halt = 1;
return 0;
} else if (!strcmp(str, "nomwait")) {
/*
* If the boot option of "idle=nomwait" is added,
* it means that mwait will be disabled for CPU C2/C3
* states. In such case it won't touch the variable
* of boot_option_idle_override.
*/
idle_nomwait = 1;
return 0;
} else
return -1;
boot_option_idle_override = 1;
return 0;
}
early_param("idle", idle_setup);