| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Spin and read/write lock operations. |
| 3 | * |
| 4 | * Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM |
| 5 | * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM |
| 6 | * Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM |
| 7 | * Rework to support virtual processors |
| 8 | * |
| 9 | * This program is free software; you can redistribute it and/or |
| 10 | * modify it under the terms of the GNU General Public License |
| 11 | * as published by the Free Software Foundation; either version |
| 12 | * 2 of the License, or (at your option) any later version. |
| 13 | */ |
| 14 | |
| 15 | #include <linux/kernel.h> |
| 16 | #include <linux/spinlock.h> |
| 17 | #include <linux/export.h> |
| 18 | #include <linux/smp.h> |
| 19 | |
| 20 | /* waiting for a spinlock... */ |
| 21 | #if defined(CONFIG_PPC_SPLPAR) |
| 22 | #include <asm/hvcall.h> |
| 23 | #include <asm/smp.h> |
| 24 | |
| 25 | void __spin_yield(arch_spinlock_t *lock) |
| 26 | { |
| 27 | unsigned int lock_value, holder_cpu, yield_count; |
| 28 | |
| 29 | lock_value = lock->slock; |
| 30 | if (lock_value == 0) |
| 31 | return; |
| 32 | holder_cpu = lock_value & 0xffff; |
| 33 | BUG_ON(holder_cpu >= NR_CPUS); |
| 34 | yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); |
| 35 | if ((yield_count & 1) == 0) |
| 36 | return; /* virtual cpu is currently running */ |
| 37 | rmb(); |
| 38 | if (lock->slock != lock_value) |
| 39 | return; /* something has changed */ |
| 40 | plpar_hcall_norets(H_CONFER, |
| 41 | get_hard_smp_processor_id(holder_cpu), yield_count); |
| 42 | } |
| 43 | EXPORT_SYMBOL_GPL(__spin_yield); |
| 44 | |
| 45 | /* |
| 46 | * Waiting for a read lock or a write lock on a rwlock... |
| 47 | * This turns out to be the same for read and write locks, since |
| 48 | * we only know the holder if it is write-locked. |
| 49 | */ |
| 50 | void __rw_yield(arch_rwlock_t *rw) |
| 51 | { |
| 52 | int lock_value; |
| 53 | unsigned int holder_cpu, yield_count; |
| 54 | |
| 55 | lock_value = rw->lock; |
| 56 | if (lock_value >= 0) |
| 57 | return; /* no write lock at present */ |
| 58 | holder_cpu = lock_value & 0xffff; |
| 59 | BUG_ON(holder_cpu >= NR_CPUS); |
| 60 | yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count); |
| 61 | if ((yield_count & 1) == 0) |
| 62 | return; /* virtual cpu is currently running */ |
| 63 | rmb(); |
| 64 | if (rw->lock != lock_value) |
| 65 | return; /* something has changed */ |
| 66 | plpar_hcall_norets(H_CONFER, |
| 67 | get_hard_smp_processor_id(holder_cpu), yield_count); |
| 68 | } |
| 69 | #endif |