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0b0ed657fe
The current code is rather complex and caused a lot of subtle and hard to debug bugs in the past. Simplify the code by calling the system_call handler with interrupts disabled, save machine state, and re-enable them later. This requires significant changes to the machine check handling code as well. When the machine check interrupt arrived while being in kernel mode the new code will signal pending machine checks with a SIGP external call. When userspace was interrupted, the handler will switch to the kernel stack and directly execute s390_handle_mcck(). Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
137 lines
3.4 KiB
C
137 lines
3.4 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/kprobes.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 <linux/sched/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 enabled_wait(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 long idle_time;
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unsigned long psw_mask, flags;
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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 | PSW_MASK_DAT |
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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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local_irq_save(flags);
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/* Call the assembler magic in entry.S */
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psw_idle(idle, psw_mask);
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local_irq_restore(flags);
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/* Account time spent with enabled wait psw loaded as idle time. */
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write_seqcount_begin(&idle->seqcount);
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idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
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idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
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idle->idle_time += idle_time;
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idle->idle_count++;
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account_idle_time(cputime_to_nsecs(idle_time));
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write_seqcount_end(&idle->seqcount);
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}
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NOKPROBE_SYMBOL(enabled_wait);
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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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unsigned long long idle_count;
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unsigned int seq;
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do {
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seq = read_seqcount_begin(&idle->seqcount);
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idle_count = READ_ONCE(idle->idle_count);
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if (READ_ONCE(idle->clock_idle_enter))
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idle_count++;
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} while (read_seqcount_retry(&idle->seqcount, seq));
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return sprintf(buf, "%llu\n", 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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unsigned long long now, idle_time, idle_enter, idle_exit, in_idle;
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struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
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unsigned int seq;
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do {
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seq = read_seqcount_begin(&idle->seqcount);
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idle_time = READ_ONCE(idle->idle_time);
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idle_enter = READ_ONCE(idle->clock_idle_enter);
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idle_exit = READ_ONCE(idle->clock_idle_exit);
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} while (read_seqcount_retry(&idle->seqcount, seq));
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in_idle = 0;
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now = get_tod_clock();
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if (idle_enter) {
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if (idle_exit) {
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in_idle = idle_exit - idle_enter;
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} else if (now > idle_enter) {
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in_idle = now - idle_enter;
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}
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}
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idle_time += in_idle;
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return sprintf(buf, "%llu\n", 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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u64 arch_cpu_idle_time(int cpu)
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{
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struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
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unsigned long long now, idle_enter, idle_exit, in_idle;
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unsigned int seq;
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do {
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seq = read_seqcount_begin(&idle->seqcount);
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idle_enter = READ_ONCE(idle->clock_idle_enter);
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idle_exit = READ_ONCE(idle->clock_idle_exit);
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} while (read_seqcount_retry(&idle->seqcount, seq));
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in_idle = 0;
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now = get_tod_clock();
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if (idle_enter) {
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if (idle_exit) {
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in_idle = idle_exit - idle_enter;
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} else if (now > idle_enter) {
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in_idle = now - idle_enter;
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}
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}
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return cputime_to_nsecs(in_idle);
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}
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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(void)
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{
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enabled_wait();
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local_irq_enable();
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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 arch_cpu_idle_dead(void)
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{
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cpu_die();
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}
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