forked from Minki/linux
54b933c6c9
Move the loop-invariant calculation of 'cpu' in do_idle() out of the loop body, because the current CPU is always constant. This improves the generated code both on x86-64 and ARM64: x86-64: Before patch (execution in loop): 864: 0f ae e8 lfence 867: 65 8b 05 c2 38 f1 7e mov %gs:0x7ef138c2(%rip),%eax 86e: 89 c0 mov %eax,%eax 870: 48 0f a3 05 68 19 08 bt %rax,0x1081968(%rip) 877: 01 After patch (execution in loop): 872: 0f ae e8 lfence 875: 4c 0f a3 25 63 19 08 bt %r12,0x1081963(%rip) 87c: 01 ARM64: Before patch (execution in loop): c58: d5033d9f dsb ld c5c: d538d080 mrs x0, tpidr_el1 c60: b8606a61 ldr w1, [x19,x0] c64: 1100fc20 add w0, w1, #0x3f c68: 7100003f cmp w1, #0x0 c6c: 1a81b000 csel w0, w0, w1, lt c70: 13067c00 asr w0, w0, #6 c74: 93407c00 sxtw x0, w0 c78: f8607a80 ldr x0, [x20,x0,lsl #3] c7c: 9ac12401 lsr x1, x0, x1 c80: 36000581 tbz w1, #0, d30 <do_idle+0x128> After patch (execution in loop): c84: d5033d9f dsb ld c88: f9400260 ldr x0, [x19] c8c: ea14001f tst x0, x20 c90: 54000580 b.eq d40 <do_idle+0x138> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com> [ Rewrote the title and the changelog. ] Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: huawei.libin@huawei.com Cc: xiexiuqi@huawei.com Link: http://lkml.kernel.org/r/1508930907-107755-1-git-send-email-cj.chengjian@huawei.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
353 lines
8.6 KiB
C
353 lines
8.6 KiB
C
/*
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* Generic entry point for the idle threads
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*/
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#include <linux/sched.h>
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#include <linux/sched/idle.h>
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#include <linux/cpu.h>
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#include <linux/cpuidle.h>
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#include <linux/cpuhotplug.h>
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#include <linux/tick.h>
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#include <linux/mm.h>
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#include <linux/stackprotector.h>
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#include <linux/suspend.h>
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#include <linux/livepatch.h>
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#include <asm/tlb.h>
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#include <trace/events/power.h>
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#include "sched.h"
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/* Linker adds these: start and end of __cpuidle functions */
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extern char __cpuidle_text_start[], __cpuidle_text_end[];
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/**
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* sched_idle_set_state - Record idle state for the current CPU.
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* @idle_state: State to record.
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*/
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void sched_idle_set_state(struct cpuidle_state *idle_state)
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{
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idle_set_state(this_rq(), idle_state);
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}
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static int __read_mostly cpu_idle_force_poll;
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void cpu_idle_poll_ctrl(bool enable)
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{
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if (enable) {
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cpu_idle_force_poll++;
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} else {
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cpu_idle_force_poll--;
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WARN_ON_ONCE(cpu_idle_force_poll < 0);
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}
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}
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#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
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static int __init cpu_idle_poll_setup(char *__unused)
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{
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cpu_idle_force_poll = 1;
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return 1;
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}
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__setup("nohlt", cpu_idle_poll_setup);
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static int __init cpu_idle_nopoll_setup(char *__unused)
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{
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cpu_idle_force_poll = 0;
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return 1;
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}
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__setup("hlt", cpu_idle_nopoll_setup);
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#endif
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static noinline int __cpuidle cpu_idle_poll(void)
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{
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rcu_idle_enter();
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trace_cpu_idle_rcuidle(0, smp_processor_id());
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local_irq_enable();
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stop_critical_timings();
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while (!tif_need_resched() &&
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(cpu_idle_force_poll || tick_check_broadcast_expired()))
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cpu_relax();
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start_critical_timings();
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trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
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rcu_idle_exit();
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return 1;
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}
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/* Weak implementations for optional arch specific functions */
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void __weak arch_cpu_idle_prepare(void) { }
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void __weak arch_cpu_idle_enter(void) { }
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void __weak arch_cpu_idle_exit(void) { }
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void __weak arch_cpu_idle_dead(void) { }
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void __weak arch_cpu_idle(void)
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{
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cpu_idle_force_poll = 1;
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local_irq_enable();
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}
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/**
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* default_idle_call - Default CPU idle routine.
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*
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* To use when the cpuidle framework cannot be used.
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*/
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void __cpuidle default_idle_call(void)
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{
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if (current_clr_polling_and_test()) {
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local_irq_enable();
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} else {
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stop_critical_timings();
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arch_cpu_idle();
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start_critical_timings();
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}
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}
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static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
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int next_state)
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{
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/*
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* The idle task must be scheduled, it is pointless to go to idle, just
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* update no idle residency and return.
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*/
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if (current_clr_polling_and_test()) {
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dev->last_residency = 0;
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local_irq_enable();
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return -EBUSY;
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}
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/*
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* Enter the idle state previously returned by the governor decision.
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* This function will block until an interrupt occurs and will take
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* care of re-enabling the local interrupts
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*/
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return cpuidle_enter(drv, dev, next_state);
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}
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/**
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* cpuidle_idle_call - the main idle function
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*
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* NOTE: no locks or semaphores should be used here
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*
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* On archs that support TIF_POLLING_NRFLAG, is called with polling
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* set, and it returns with polling set. If it ever stops polling, it
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* must clear the polling bit.
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*/
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static void cpuidle_idle_call(void)
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{
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struct cpuidle_device *dev = cpuidle_get_device();
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struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
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int next_state, entered_state;
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/*
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* Check if the idle task must be rescheduled. If it is the
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* case, exit the function after re-enabling the local irq.
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*/
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if (need_resched()) {
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local_irq_enable();
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return;
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}
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/*
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* Tell the RCU framework we are entering an idle section,
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* so no more rcu read side critical sections and one more
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* step to the grace period
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*/
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rcu_idle_enter();
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if (cpuidle_not_available(drv, dev)) {
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default_idle_call();
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goto exit_idle;
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}
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/*
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* Suspend-to-idle ("s2idle") is a system state in which all user space
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* has been frozen, all I/O devices have been suspended and the only
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* activity happens here and in iterrupts (if any). In that case bypass
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* the cpuidle governor and go stratight for the deepest idle state
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* available. Possibly also suspend the local tick and the entire
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* timekeeping to prevent timer interrupts from kicking us out of idle
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* until a proper wakeup interrupt happens.
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*/
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if (idle_should_enter_s2idle() || dev->use_deepest_state) {
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if (idle_should_enter_s2idle()) {
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entered_state = cpuidle_enter_s2idle(drv, dev);
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if (entered_state > 0) {
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local_irq_enable();
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goto exit_idle;
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}
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}
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next_state = cpuidle_find_deepest_state(drv, dev);
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call_cpuidle(drv, dev, next_state);
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} else {
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/*
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* Ask the cpuidle framework to choose a convenient idle state.
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*/
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next_state = cpuidle_select(drv, dev);
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entered_state = call_cpuidle(drv, dev, next_state);
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/*
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* Give the governor an opportunity to reflect on the outcome
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*/
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cpuidle_reflect(dev, entered_state);
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}
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exit_idle:
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__current_set_polling();
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/*
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* It is up to the idle functions to reenable local interrupts
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*/
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if (WARN_ON_ONCE(irqs_disabled()))
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local_irq_enable();
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rcu_idle_exit();
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}
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/*
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* Generic idle loop implementation
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*
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* Called with polling cleared.
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*/
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static void do_idle(void)
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{
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int cpu = smp_processor_id();
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/*
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* If the arch has a polling bit, we maintain an invariant:
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*
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* Our polling bit is clear if we're not scheduled (i.e. if rq->curr !=
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* rq->idle). This means that, if rq->idle has the polling bit set,
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* then setting need_resched is guaranteed to cause the CPU to
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* reschedule.
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*/
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__current_set_polling();
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tick_nohz_idle_enter();
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while (!need_resched()) {
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check_pgt_cache();
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rmb();
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if (cpu_is_offline(cpu)) {
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cpuhp_report_idle_dead();
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arch_cpu_idle_dead();
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}
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local_irq_disable();
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arch_cpu_idle_enter();
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/*
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* In poll mode we reenable interrupts and spin. Also if we
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* detected in the wakeup from idle path that the tick
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* broadcast device expired for us, we don't want to go deep
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* idle as we know that the IPI is going to arrive right away.
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*/
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if (cpu_idle_force_poll || tick_check_broadcast_expired())
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cpu_idle_poll();
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else
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cpuidle_idle_call();
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arch_cpu_idle_exit();
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}
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/*
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* Since we fell out of the loop above, we know TIF_NEED_RESCHED must
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* be set, propagate it into PREEMPT_NEED_RESCHED.
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*
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* This is required because for polling idle loops we will not have had
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* an IPI to fold the state for us.
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*/
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preempt_set_need_resched();
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tick_nohz_idle_exit();
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__current_clr_polling();
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/*
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* We promise to call sched_ttwu_pending() and reschedule if
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* need_resched() is set while polling is set. That means that clearing
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* polling needs to be visible before doing these things.
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*/
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smp_mb__after_atomic();
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sched_ttwu_pending();
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schedule_idle();
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if (unlikely(klp_patch_pending(current)))
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klp_update_patch_state(current);
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}
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bool cpu_in_idle(unsigned long pc)
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{
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return pc >= (unsigned long)__cpuidle_text_start &&
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pc < (unsigned long)__cpuidle_text_end;
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}
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struct idle_timer {
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struct hrtimer timer;
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int done;
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};
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static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
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{
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struct idle_timer *it = container_of(timer, struct idle_timer, timer);
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WRITE_ONCE(it->done, 1);
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set_tsk_need_resched(current);
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return HRTIMER_NORESTART;
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}
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void play_idle(unsigned long duration_ms)
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{
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struct idle_timer it;
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/*
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* Only FIFO tasks can disable the tick since they don't need the forced
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* preemption.
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*/
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WARN_ON_ONCE(current->policy != SCHED_FIFO);
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WARN_ON_ONCE(current->nr_cpus_allowed != 1);
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WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
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WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
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WARN_ON_ONCE(!duration_ms);
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rcu_sleep_check();
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preempt_disable();
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current->flags |= PF_IDLE;
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cpuidle_use_deepest_state(true);
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it.done = 0;
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hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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it.timer.function = idle_inject_timer_fn;
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hrtimer_start(&it.timer, ms_to_ktime(duration_ms), HRTIMER_MODE_REL_PINNED);
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while (!READ_ONCE(it.done))
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do_idle();
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cpuidle_use_deepest_state(false);
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current->flags &= ~PF_IDLE;
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preempt_fold_need_resched();
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preempt_enable();
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}
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EXPORT_SYMBOL_GPL(play_idle);
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void cpu_startup_entry(enum cpuhp_state state)
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{
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/*
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* This #ifdef needs to die, but it's too late in the cycle to
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* make this generic (arm and sh have never invoked the canary
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* init for the non boot cpus!). Will be fixed in 3.11
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*/
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#ifdef CONFIG_X86
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/*
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* If we're the non-boot CPU, nothing set the stack canary up
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* for us. The boot CPU already has it initialized but no harm
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* in doing it again. This is a good place for updating it, as
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* we wont ever return from this function (so the invalid
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* canaries already on the stack wont ever trigger).
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*/
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boot_init_stack_canary();
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#endif
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arch_cpu_idle_prepare();
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cpuhp_online_idle(state);
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while (1)
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do_idle();
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}
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