linux/arch/powerpc/kernel/idle.c
Signed-off-by: Darren Hart a7c2bb8279 powerpc: Re-enable preemption before cpu_die()
start_secondary() is called shortly after _start and also via

cpu_idle()->cpu_die()->pseries_mach_cpu_die()

start_secondary() expects a preempt_count() of 0. pseries_mach_cpu_die() is
called via the cpu_idle() routine with preemption disabled, resulting in the
following repeating message during rapid cpu offline/online tests
with CONFIG_PREEMPT=y:

BUG: scheduling while atomic: swapper/0/0x00000002
Modules linked in: autofs4 binfmt_misc dm_mirror dm_region_hash dm_log [last unloaded: scsi_wait_scan]
Call Trace:
[c00000010e7079c0] [c0000000000133ec] .show_stack+0xd8/0x218 (unreliable)
[c00000010e707aa0] [c0000000006a47f0] .dump_stack+0x28/0x3c
[c00000010e707b20] [c00000000006e7a4] .__schedule_bug+0x7c/0x9c
[c00000010e707bb0] [c000000000699d9c] .schedule+0x104/0x800
[c00000010e707cd0] [c000000000015b24] .cpu_idle+0x1c4/0x1d8
[c00000010e707d70] [c0000000006aa1b4] .start_secondary+0x398/0x3d4
[c00000010e707e30] [c000000000008278] .start_secondary_resume+0x10/0x14

Move the cpu_die() call inside the existing preemption enabled block of
cpu_idle(). This is safe as the idle task is affined to a single CPU so the
debug_smp_processor_id() tests (from cpu_should_die()) won't trigger as we are
in a "migration disabled" region.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Acked-by: Will Schmidt <will_schmidt@vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nathan Fontenot <nfont@austin.ibm.com>
Cc: Robert Jennings <rcj@linux.vnet.ibm.com>
Cc: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2010-08-24 15:26:29 +10:00

138 lines
3 KiB
C

/*
* Idle daemon for PowerPC. Idle daemon will handle any action
* that needs to be taken when the system becomes idle.
*
* Originally written by Cort Dougan (cort@cs.nmt.edu).
* Subsequent 32-bit hacking by Tom Rini, Armin Kuster,
* Paul Mackerras and others.
*
* iSeries supported added by Mike Corrigan <mikejc@us.ibm.com>
*
* Additional shared processor, SMT, and firmware support
* Copyright (c) 2003 Dave Engebretsen <engebret@us.ibm.com>
*
* 32-bit and 64-bit versions merged by Paul Mackerras <paulus@samba.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/cpu.h>
#include <linux/sysctl.h>
#include <linux/tick.h>
#include <asm/system.h>
#include <asm/processor.h>
#include <asm/cputable.h>
#include <asm/time.h>
#include <asm/machdep.h>
#include <asm/smp.h>
#ifdef CONFIG_HOTPLUG_CPU
#define cpu_should_die() cpu_is_offline(smp_processor_id())
#else
#define cpu_should_die() 0
#endif
static int __init powersave_off(char *arg)
{
ppc_md.power_save = NULL;
return 0;
}
__setup("powersave=off", powersave_off);
/*
* The body of the idle task.
*/
void cpu_idle(void)
{
if (ppc_md.idle_loop)
ppc_md.idle_loop(); /* doesn't return */
set_thread_flag(TIF_POLLING_NRFLAG);
while (1) {
tick_nohz_stop_sched_tick(1);
while (!need_resched() && !cpu_should_die()) {
ppc64_runlatch_off();
if (ppc_md.power_save) {
clear_thread_flag(TIF_POLLING_NRFLAG);
/*
* smp_mb is so clearing of TIF_POLLING_NRFLAG
* is ordered w.r.t. need_resched() test.
*/
smp_mb();
local_irq_disable();
/* Don't trace irqs off for idle */
stop_critical_timings();
/* check again after disabling irqs */
if (!need_resched() && !cpu_should_die())
ppc_md.power_save();
start_critical_timings();
local_irq_enable();
set_thread_flag(TIF_POLLING_NRFLAG);
} else {
/*
* Go into low thread priority and possibly
* low power mode.
*/
HMT_low();
HMT_very_low();
}
}
HMT_medium();
ppc64_runlatch_on();
tick_nohz_restart_sched_tick();
preempt_enable_no_resched();
if (cpu_should_die())
cpu_die();
schedule();
preempt_disable();
}
}
int powersave_nap;
#ifdef CONFIG_SYSCTL
/*
* Register the sysctl to set/clear powersave_nap.
*/
static ctl_table powersave_nap_ctl_table[]={
{
.procname = "powersave-nap",
.data = &powersave_nap,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{}
};
static ctl_table powersave_nap_sysctl_root[] = {
{
.procname = "kernel",
.mode = 0555,
.child = powersave_nap_ctl_table,
},
{}
};
static int __init
register_powersave_nap_sysctl(void)
{
register_sysctl_table(powersave_nap_sysctl_root);
return 0;
}
__initcall(register_powersave_nap_sysctl);
#endif