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071c44e427
Before commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead()
return"), in Xen, when a previously offlined CPU was brought back
online, it unexpectedly resumed execution where it left off in the
middle of the idle loop.
There were some hacks to make that work, but the behavior was surprising
as do_idle() doesn't expect an offlined CPU to return from the dead (in
arch_cpu_idle_dead()).
Now that Xen has been fixed, and the arch-specific implementations of
arch_cpu_idle_dead() also don't return, give it a __noreturn attribute.
This will cause the compiler to complain if an arch-specific
implementation might return. It also improves code generation for both
caller and callee.
Also fixes the following warning:
vmlinux.o: warning: objtool: do_idle+0x25f: unreachable instruction
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/60d527353da8c99d4cf13b6473131d46719ed16d.1676358308.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
95 lines
2.5 KiB
C
95 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Idle functions for s390.
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*
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* Copyright IBM Corp. 2014
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*
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
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*/
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#include <linux/kernel.h>
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#include <linux/kernel_stat.h>
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#include <linux/notifier.h>
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#include <linux/init.h>
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#include <linux/cpu.h>
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#include <trace/events/power.h>
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#include <asm/cpu_mf.h>
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#include <asm/cputime.h>
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#include <asm/nmi.h>
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#include <asm/smp.h>
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#include "entry.h"
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static DEFINE_PER_CPU(struct s390_idle_data, s390_idle);
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void account_idle_time_irq(void)
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{
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struct s390_idle_data *idle = this_cpu_ptr(&s390_idle);
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unsigned long idle_time;
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u64 cycles_new[8];
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int i;
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if (smp_cpu_mtid) {
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stcctm(MT_DIAG, smp_cpu_mtid, cycles_new);
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for (i = 0; i < smp_cpu_mtid; i++)
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this_cpu_add(mt_cycles[i], cycles_new[i] - idle->mt_cycles_enter[i]);
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}
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idle_time = S390_lowcore.int_clock - idle->clock_idle_enter;
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S390_lowcore.steal_timer += idle->clock_idle_enter - S390_lowcore.last_update_clock;
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S390_lowcore.last_update_clock = S390_lowcore.int_clock;
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S390_lowcore.system_timer += S390_lowcore.last_update_timer - idle->timer_idle_enter;
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S390_lowcore.last_update_timer = S390_lowcore.sys_enter_timer;
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/* Account time spent with enabled wait psw loaded as idle time. */
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WRITE_ONCE(idle->idle_time, READ_ONCE(idle->idle_time) + idle_time);
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WRITE_ONCE(idle->idle_count, READ_ONCE(idle->idle_count) + 1);
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account_idle_time(cputime_to_nsecs(idle_time));
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}
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void noinstr arch_cpu_idle(void)
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{
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struct s390_idle_data *idle = this_cpu_ptr(&s390_idle);
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unsigned long psw_mask;
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/* Wait for external, I/O or machine check interrupt. */
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psw_mask = PSW_KERNEL_BITS | PSW_MASK_WAIT |
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PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
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clear_cpu_flag(CIF_NOHZ_DELAY);
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/* psw_idle() returns with interrupts disabled. */
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psw_idle(idle, psw_mask);
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}
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static ssize_t show_idle_count(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
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return sysfs_emit(buf, "%lu\n", READ_ONCE(idle->idle_count));
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}
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DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL);
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static ssize_t show_idle_time(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
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return sysfs_emit(buf, "%lu\n", READ_ONCE(idle->idle_time) >> 12);
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}
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DEVICE_ATTR(idle_time_us, 0444, show_idle_time, NULL);
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void arch_cpu_idle_enter(void)
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{
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}
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void arch_cpu_idle_exit(void)
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{
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}
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void __noreturn arch_cpu_idle_dead(void)
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{
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cpu_die();
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}
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