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1f8c82ab1b
If CONFIG_SMP=n, <linux/smp.h> does not include <asm/smp.h>, causing: drivers/cpufreq/ppc-corenet-cpufreq.c: In function 'corenet_cpufreq_cpu_init': drivers/cpufreq/ppc-corenet-cpufreq.c:173:3: error: implicit declaration of function 'get_hard_smp_processor_id' [-Werror=implicit-funcuresh E. Warrier" <warrier@linux.vnet.ibm.com> X-Patchwork-Id: 443703 Message-Id: <54EE5989.7010800@linux.vnet.ibm.com> To: linuxppc-dev@ozlabs.org Date: Wed, 25 Feb 2015 17:23:53 -0600 Export __spin_yield so that the arch_spin_unlock() function can be invoked from a module. This will be required for modules where we want to take a lock that is also is acquired in hypervisor real mode. Because we want to avoid running any lockdep code (which may not be safe in real mode), this lock needs to be an arch_spinlock_t instead of a normal spinlock. Signed-off-by: Suresh Warrier <warrier@linux.vnet.ibm.com> Acked-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
87 lines
2.3 KiB
C
87 lines
2.3 KiB
C
/*
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* Spin and read/write lock operations.
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*
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* Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
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* Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
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* Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
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* Rework to support virtual processors
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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/kernel.h>
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#include <linux/spinlock.h>
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#include <linux/export.h>
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#include <linux/stringify.h>
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#include <linux/smp.h>
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/* waiting for a spinlock... */
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#if defined(CONFIG_PPC_SPLPAR)
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#include <asm/hvcall.h>
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#include <asm/smp.h>
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void __spin_yield(arch_spinlock_t *lock)
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{
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unsigned int lock_value, holder_cpu, yield_count;
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lock_value = lock->slock;
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if (lock_value == 0)
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return;
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holder_cpu = lock_value & 0xffff;
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BUG_ON(holder_cpu >= NR_CPUS);
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yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
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if ((yield_count & 1) == 0)
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return; /* virtual cpu is currently running */
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rmb();
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if (lock->slock != lock_value)
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return; /* something has changed */
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plpar_hcall_norets(H_CONFER,
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get_hard_smp_processor_id(holder_cpu), yield_count);
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}
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EXPORT_SYMBOL_GPL(__spin_yield);
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/*
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* Waiting for a read lock or a write lock on a rwlock...
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* This turns out to be the same for read and write locks, since
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* we only know the holder if it is write-locked.
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*/
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void __rw_yield(arch_rwlock_t *rw)
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{
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int lock_value;
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unsigned int holder_cpu, yield_count;
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lock_value = rw->lock;
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if (lock_value >= 0)
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return; /* no write lock at present */
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holder_cpu = lock_value & 0xffff;
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BUG_ON(holder_cpu >= NR_CPUS);
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yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
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if ((yield_count & 1) == 0)
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return; /* virtual cpu is currently running */
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rmb();
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if (rw->lock != lock_value)
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return; /* something has changed */
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plpar_hcall_norets(H_CONFER,
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get_hard_smp_processor_id(holder_cpu), yield_count);
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}
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#endif
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void arch_spin_unlock_wait(arch_spinlock_t *lock)
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{
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smp_mb();
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while (lock->slock) {
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HMT_low();
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if (SHARED_PROCESSOR)
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__spin_yield(lock);
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}
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HMT_medium();
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smp_mb();
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}
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EXPORT_SYMBOL(arch_spin_unlock_wait);
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