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830eec2467
The arm boot_lock is used by the secondary processor startup code. The locking
task is the idle thread, which has idle->sched_class == &idle_sched_class.
idle_sched_class->enqueue_task == NULL, so if the idle task blocks on the
lock, the attempt to wake it when the lock becomes available will fail:
try_to_wake_up()
...
activate_task()
enqueue_task()
p->sched_class->enqueue_task(rq, p, flags)
Fix by converting boot_lock to a raw spin lock.
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Frank Rowand <frank.rowand@am.sony.com>
Link: http://lkml.kernel.org/r/4E77B952.3010606@am.sony.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
94 lines
2.2 KiB
C
94 lines
2.2 KiB
C
/*
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* linux/arch/arm/plat-versatile/platsmp.c
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*
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* Copyright (C) 2002 ARM Ltd.
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/init.h>
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#include <linux/errno.h>
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/jiffies.h>
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#include <linux/smp.h>
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#include <asm/cacheflush.h>
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#include <asm/smp_plat.h>
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#include <plat/platsmp.h>
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/*
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* Write pen_release in a way that is guaranteed to be visible to all
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* observers, irrespective of whether they're taking part in coherency
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* or not. This is necessary for the hotplug code to work reliably.
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*/
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static void write_pen_release(int val)
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{
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pen_release = val;
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smp_wmb();
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sync_cache_w(&pen_release);
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}
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static DEFINE_RAW_SPINLOCK(boot_lock);
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void versatile_secondary_init(unsigned int cpu)
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{
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/*
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* let the primary processor know we're out of the
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* pen, then head off into the C entry point
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*/
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write_pen_release(-1);
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/*
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* Synchronise with the boot thread.
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*/
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raw_spin_lock(&boot_lock);
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raw_spin_unlock(&boot_lock);
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}
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int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
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{
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unsigned long timeout;
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/*
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* Set synchronisation state between this boot processor
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* and the secondary one
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*/
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raw_spin_lock(&boot_lock);
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/*
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* This is really belt and braces; we hold unintended secondary
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* CPUs in the holding pen until we're ready for them. However,
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* since we haven't sent them a soft interrupt, they shouldn't
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* be there.
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*/
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write_pen_release(cpu_logical_map(cpu));
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/*
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* Send the secondary CPU a soft interrupt, thereby causing
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* the boot monitor to read the system wide flags register,
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* and branch to the address found there.
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*/
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arch_send_wakeup_ipi_mask(cpumask_of(cpu));
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timeout = jiffies + (1 * HZ);
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while (time_before(jiffies, timeout)) {
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smp_rmb();
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if (pen_release == -1)
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break;
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udelay(10);
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}
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/*
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* now the secondary core is starting up let it run its
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* calibrations, then wait for it to finish
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*/
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raw_spin_unlock(&boot_lock);
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return pen_release != -1 ? -ENOSYS : 0;
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}
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