mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 02:39:48 +00:00
![Peter Zijlstra](/assets/img/avatar_default.png)
With various drivers wanting to inject idle time; we get people calling idle routines outside of the idle loop proper. Therefore we need to be extra careful about not missing TIF_NEED_RESCHED -> PREEMPT_NEED_RESCHED propagations. While looking at this, I also realized there's a small window in the existing idle loop where we can miss TIF_NEED_RESCHED; when it hits right after the tif_need_resched() test at the end of the loop but right before the need_resched() test at the start of the loop. So move preempt_fold_need_resched() out of the loop where we're guaranteed to have TIF_NEED_RESCHED set. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-x9jgh45oeayzajz2mjt0y7d6@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
144 lines
3.3 KiB
C
144 lines
3.3 KiB
C
/*
|
|
* Generic entry point for the idle threads
|
|
*/
|
|
#include <linux/sched.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/tick.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/stackprotector.h>
|
|
|
|
#include <asm/tlb.h>
|
|
|
|
#include <trace/events/power.h>
|
|
|
|
static int __read_mostly cpu_idle_force_poll;
|
|
|
|
void cpu_idle_poll_ctrl(bool enable)
|
|
{
|
|
if (enable) {
|
|
cpu_idle_force_poll++;
|
|
} else {
|
|
cpu_idle_force_poll--;
|
|
WARN_ON_ONCE(cpu_idle_force_poll < 0);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
|
|
static int __init cpu_idle_poll_setup(char *__unused)
|
|
{
|
|
cpu_idle_force_poll = 1;
|
|
return 1;
|
|
}
|
|
__setup("nohlt", cpu_idle_poll_setup);
|
|
|
|
static int __init cpu_idle_nopoll_setup(char *__unused)
|
|
{
|
|
cpu_idle_force_poll = 0;
|
|
return 1;
|
|
}
|
|
__setup("hlt", cpu_idle_nopoll_setup);
|
|
#endif
|
|
|
|
static inline int cpu_idle_poll(void)
|
|
{
|
|
rcu_idle_enter();
|
|
trace_cpu_idle_rcuidle(0, smp_processor_id());
|
|
local_irq_enable();
|
|
while (!tif_need_resched())
|
|
cpu_relax();
|
|
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
|
|
rcu_idle_exit();
|
|
return 1;
|
|
}
|
|
|
|
/* Weak implementations for optional arch specific functions */
|
|
void __weak arch_cpu_idle_prepare(void) { }
|
|
void __weak arch_cpu_idle_enter(void) { }
|
|
void __weak arch_cpu_idle_exit(void) { }
|
|
void __weak arch_cpu_idle_dead(void) { }
|
|
void __weak arch_cpu_idle(void)
|
|
{
|
|
cpu_idle_force_poll = 1;
|
|
local_irq_enable();
|
|
}
|
|
|
|
/*
|
|
* Generic idle loop implementation
|
|
*/
|
|
static void cpu_idle_loop(void)
|
|
{
|
|
while (1) {
|
|
tick_nohz_idle_enter();
|
|
|
|
while (!need_resched()) {
|
|
check_pgt_cache();
|
|
rmb();
|
|
|
|
if (cpu_is_offline(smp_processor_id()))
|
|
arch_cpu_idle_dead();
|
|
|
|
local_irq_disable();
|
|
arch_cpu_idle_enter();
|
|
|
|
/*
|
|
* In poll mode we reenable interrupts and spin.
|
|
*
|
|
* Also if we detected in the wakeup from idle
|
|
* path that the tick broadcast device expired
|
|
* for us, we don't want to go deep idle as we
|
|
* know that the IPI is going to arrive right
|
|
* away
|
|
*/
|
|
if (cpu_idle_force_poll || tick_check_broadcast_expired()) {
|
|
cpu_idle_poll();
|
|
} else {
|
|
if (!current_clr_polling_and_test()) {
|
|
stop_critical_timings();
|
|
rcu_idle_enter();
|
|
arch_cpu_idle();
|
|
WARN_ON_ONCE(irqs_disabled());
|
|
rcu_idle_exit();
|
|
start_critical_timings();
|
|
} else {
|
|
local_irq_enable();
|
|
}
|
|
__current_set_polling();
|
|
}
|
|
arch_cpu_idle_exit();
|
|
}
|
|
|
|
/*
|
|
* Since we fell out of the loop above, we know
|
|
* TIF_NEED_RESCHED must be set, propagate it into
|
|
* PREEMPT_NEED_RESCHED.
|
|
*
|
|
* This is required because for polling idle loops we will
|
|
* not have had an IPI to fold the state for us.
|
|
*/
|
|
preempt_set_need_resched();
|
|
tick_nohz_idle_exit();
|
|
schedule_preempt_disabled();
|
|
}
|
|
}
|
|
|
|
void cpu_startup_entry(enum cpuhp_state state)
|
|
{
|
|
/*
|
|
* This #ifdef needs to die, but it's too late in the cycle to
|
|
* make this generic (arm and sh have never invoked the canary
|
|
* init for the non boot cpus!). Will be fixed in 3.11
|
|
*/
|
|
#ifdef CONFIG_X86
|
|
/*
|
|
* If we're the non-boot CPU, nothing set the stack canary up
|
|
* for us. The boot CPU already has it initialized but no harm
|
|
* in doing it again. This is a good place for updating it, as
|
|
* we wont ever return from this function (so the invalid
|
|
* canaries already on the stack wont ever trigger).
|
|
*/
|
|
boot_init_stack_canary();
|
|
#endif
|
|
__current_set_polling();
|
|
arch_cpu_idle_prepare();
|
|
cpu_idle_loop();
|
|
}
|