| 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
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| 2 | /* |
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| 3 | * Spin and read/write lock operations. |
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| 4 | * |
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| 5 | * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM |
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| 6 | * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM |
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| 7 | * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM |
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| 8 | * Rework to support virtual processors |
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| 9 | */ |
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| 10 | |
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| 11 | #include <linux/kernel.h> |
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| 12 | #include <linux/spinlock.h> |
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| 13 | #include <linux/export.h> |
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| 14 | #include <linux/smp.h> |
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| 15 | |
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| 16 | /* waiting for a spinlock... */ |
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| 17 | #if defined(CONFIG_PPC_SPLPAR) |
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| 18 | #include <asm/hvcall.h> |
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| 19 | #include <asm/smp.h> |
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| 20 | |
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| 21 | void splpar_spin_yield(arch_spinlock_t *lock) |
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| 22 | { |
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| 23 | unsigned int lock_value, holder_cpu, yield_count; |
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| 24 | |
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| 25 | lock_value = lock->slock; |
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| 26 | if (lock_value == 0) |
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| 27 | return; |
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| 28 | holder_cpu = lock_value & 0xffff; |
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| 29 | BUG_ON(holder_cpu >= NR_CPUS); |
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| 30 | |
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| 31 | yield_count = yield_count_of(holder_cpu); |
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| 32 | if ((yield_count & 1) == 0) |
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| 33 | return; /* virtual cpu is currently running */ |
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| 34 | rmb(); |
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| 35 | if (lock->slock != lock_value) |
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| 36 | return; /* something has changed */ |
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| 37 | yield_to_preempted(holder_cpu, yield_count); |
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| 38 | } |
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| 39 | EXPORT_SYMBOL_GPL(splpar_spin_yield); |
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| 40 | |
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| 41 | /* |
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| 42 | * Waiting for a read lock or a write lock on a rwlock... |
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| 43 | * This turns out to be the same for read and write locks, since |
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| 44 | * we only know the holder if it is write-locked. |
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| 45 | */ |
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| 46 | void splpar_rw_yield(arch_rwlock_t *rw) |
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| 47 | { |
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| 48 | int lock_value; |
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| 49 | unsigned int holder_cpu, yield_count; |
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| 50 | |
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| 51 | lock_value = rw->lock; |
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| 52 | if (lock_value >= 0) |
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| 53 | return; /* no write lock at present */ |
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| 54 | holder_cpu = lock_value & 0xffff; |
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| 55 | BUG_ON(holder_cpu >= NR_CPUS); |
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| 56 | |
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| 57 | yield_count = yield_count_of(holder_cpu); |
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| 58 | if ((yield_count & 1) == 0) |
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| 59 | return; /* virtual cpu is currently running */ |
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| 60 | rmb(); |
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| 61 | if (rw->lock != lock_value) |
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| 62 | return; /* something has changed */ |
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| 63 | yield_to_preempted(holder_cpu, yield_count); |
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| 64 | } |
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| 65 | #endif |
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| 66 | |
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