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The PowerPC pSeries platform (CONFIG_PPC_PSERIES=y) enables hypervisor-call tracing for CONFIG_TRACEPOINTS=y kernels. One of the hypervisor calls that is traced is the H_CEDE call in the idle loop that tells the hypervisor that this OS instance no longer needs the current CPU. However, tracing uses RCU, so this combination of kernel configuration variables needs to avoid telling RCU about the current CPU's idleness until after the H_CEDE-entry tracing completes on the one hand, and must tell RCU that the the current CPU is no longer idle before the H_CEDE-exit tracing starts. In all other cases, it suffices to inform RCU of CPU idleness upon idle-loop entry and exit. This commit makes the required adjustments. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
151 lines
3.2 KiB
C
151 lines
3.2 KiB
C
/*
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* Idle daemon for PowerPC. Idle daemon will handle any action
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* that needs to be taken when the system becomes idle.
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*
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* Originally written by Cort Dougan (cort@cs.nmt.edu).
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* Subsequent 32-bit hacking by Tom Rini, Armin Kuster,
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* Paul Mackerras and others.
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*
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* iSeries supported added by Mike Corrigan <mikejc@us.ibm.com>
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*
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* Additional shared processor, SMT, and firmware support
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* Copyright (c) 2003 Dave Engebretsen <engebret@us.ibm.com>
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*
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* 32-bit and 64-bit versions merged by Paul Mackerras <paulus@samba.org>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/smp.h>
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#include <linux/cpu.h>
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#include <linux/sysctl.h>
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#include <linux/tick.h>
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#include <asm/system.h>
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#include <asm/processor.h>
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#include <asm/cputable.h>
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#include <asm/time.h>
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#include <asm/machdep.h>
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#include <asm/smp.h>
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#ifdef CONFIG_HOTPLUG_CPU
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#define cpu_should_die() cpu_is_offline(smp_processor_id())
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#else
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#define cpu_should_die() 0
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#endif
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static int __init powersave_off(char *arg)
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{
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ppc_md.power_save = NULL;
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return 0;
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}
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__setup("powersave=off", powersave_off);
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#if defined(CONFIG_PPC_PSERIES) && defined(CONFIG_TRACEPOINTS)
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static const bool idle_uses_rcu = 1;
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#else
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static const bool idle_uses_rcu;
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#endif
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/*
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* The body of the idle task.
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*/
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void cpu_idle(void)
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{
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if (ppc_md.idle_loop)
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ppc_md.idle_loop(); /* doesn't return */
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set_thread_flag(TIF_POLLING_NRFLAG);
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while (1) {
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if (idle_uses_rcu)
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tick_nohz_idle_enter();
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else
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tick_nohz_idle_enter_norcu();
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while (!need_resched() && !cpu_should_die()) {
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ppc64_runlatch_off();
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if (ppc_md.power_save) {
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clear_thread_flag(TIF_POLLING_NRFLAG);
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/*
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* smp_mb is so clearing of TIF_POLLING_NRFLAG
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* is ordered w.r.t. need_resched() test.
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*/
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smp_mb();
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local_irq_disable();
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/* Don't trace irqs off for idle */
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stop_critical_timings();
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/* check again after disabling irqs */
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if (!need_resched() && !cpu_should_die())
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ppc_md.power_save();
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start_critical_timings();
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local_irq_enable();
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set_thread_flag(TIF_POLLING_NRFLAG);
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} else {
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/*
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* Go into low thread priority and possibly
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* low power mode.
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*/
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HMT_low();
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HMT_very_low();
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}
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}
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HMT_medium();
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ppc64_runlatch_on();
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if (idle_uses_rcu)
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tick_nohz_idle_exit();
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else
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tick_nohz_idle_exit_norcu();
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preempt_enable_no_resched();
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if (cpu_should_die())
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cpu_die();
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schedule();
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preempt_disable();
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}
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}
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int powersave_nap;
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#ifdef CONFIG_SYSCTL
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/*
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* Register the sysctl to set/clear powersave_nap.
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*/
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static ctl_table powersave_nap_ctl_table[]={
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{
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.procname = "powersave-nap",
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.data = &powersave_nap,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{}
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};
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static ctl_table powersave_nap_sysctl_root[] = {
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{
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.procname = "kernel",
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.mode = 0555,
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.child = powersave_nap_ctl_table,
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},
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{}
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};
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static int __init
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register_powersave_nap_sysctl(void)
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{
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register_sysctl_table(powersave_nap_sysctl_root);
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return 0;
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}
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__initcall(register_powersave_nap_sysctl);
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#endif
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