9513e5e3f5
On s390 the lock value used for spinlocks consists of the lower 32 bits of the PSW that holds the lock. If this address happens to be on a four gigabyte boundary the lock is left unlocked. This allows other cpus to grab the same lock and enter a lock protected code path concurrently. In theory this can happen if the vmalloc area for the code of a module crosses a 4 GB boundary. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
156 lines
3.9 KiB
C
156 lines
3.9 KiB
C
/*
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* include/asm-s390/spinlock.h
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*
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* S390 version
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* Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
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* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
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*
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* Derived from "include/asm-i386/spinlock.h"
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*/
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#ifndef __ASM_SPINLOCK_H
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#define __ASM_SPINLOCK_H
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static inline int
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_raw_compare_and_swap(volatile unsigned int *lock,
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unsigned int old, unsigned int new)
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{
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asm volatile ("cs %0,%3,0(%4)"
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: "=d" (old), "=m" (*lock)
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: "0" (old), "d" (new), "a" (lock), "m" (*lock)
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: "cc", "memory" );
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return old;
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}
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/*
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* Simple spin lock operations. There are two variants, one clears IRQ's
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* on the local processor, one does not.
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*
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* We make no fairness assumptions. They have a cost.
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*/
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typedef struct {
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volatile unsigned int lock;
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#ifdef CONFIG_PREEMPT
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unsigned int break_lock;
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#endif
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} __attribute__ ((aligned (4))) spinlock_t;
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#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
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#define spin_lock_init(lp) do { (lp)->lock = 0; } while(0)
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#define spin_unlock_wait(lp) do { barrier(); } while(((volatile spinlock_t *)(lp))->lock)
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#define spin_is_locked(x) ((x)->lock != 0)
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#define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)
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extern void _raw_spin_lock_wait(spinlock_t *lp, unsigned int pc);
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extern int _raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc);
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static inline void _raw_spin_lock(spinlock_t *lp)
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{
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unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
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if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0))
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_raw_spin_lock_wait(lp, pc);
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}
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static inline int _raw_spin_trylock(spinlock_t *lp)
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{
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unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
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if (likely(_raw_compare_and_swap(&lp->lock, 0, pc) == 0))
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return 1;
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return _raw_spin_trylock_retry(lp, pc);
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}
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static inline void _raw_spin_unlock(spinlock_t *lp)
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{
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_raw_compare_and_swap(&lp->lock, lp->lock, 0);
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}
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/*
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* Read-write spinlocks, allowing multiple readers
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* but only one writer.
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*
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* NOTE! it is quite common to have readers in interrupts
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* but no interrupt writers. For those circumstances we
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* can "mix" irq-safe locks - any writer needs to get a
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* irq-safe write-lock, but readers can get non-irqsafe
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* read-locks.
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*/
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typedef struct {
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volatile unsigned int lock;
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volatile unsigned long owner_pc;
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#ifdef CONFIG_PREEMPT
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unsigned int break_lock;
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#endif
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} rwlock_t;
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#define RW_LOCK_UNLOCKED (rwlock_t) { 0, 0 }
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#define rwlock_init(x) do { *(x) = RW_LOCK_UNLOCKED; } while(0)
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/**
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* read_can_lock - would read_trylock() succeed?
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* @lock: the rwlock in question.
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*/
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#define read_can_lock(x) ((int)(x)->lock >= 0)
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/**
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* write_can_lock - would write_trylock() succeed?
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* @lock: the rwlock in question.
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*/
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#define write_can_lock(x) ((x)->lock == 0)
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extern void _raw_read_lock_wait(rwlock_t *lp);
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extern int _raw_read_trylock_retry(rwlock_t *lp);
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extern void _raw_write_lock_wait(rwlock_t *lp);
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extern int _raw_write_trylock_retry(rwlock_t *lp);
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static inline void _raw_read_lock(rwlock_t *rw)
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{
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unsigned int old;
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old = rw->lock & 0x7fffffffU;
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if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
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_raw_read_lock_wait(rw);
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}
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static inline void _raw_read_unlock(rwlock_t *rw)
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{
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unsigned int old, cmp;
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old = rw->lock;
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do {
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cmp = old;
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old = _raw_compare_and_swap(&rw->lock, old, old - 1);
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} while (cmp != old);
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}
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static inline void _raw_write_lock(rwlock_t *rw)
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{
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if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
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_raw_write_lock_wait(rw);
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}
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static inline void _raw_write_unlock(rwlock_t *rw)
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{
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_raw_compare_and_swap(&rw->lock, 0x80000000, 0);
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}
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static inline int _raw_read_trylock(rwlock_t *rw)
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{
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unsigned int old;
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old = rw->lock & 0x7fffffffU;
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if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
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return 1;
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return _raw_read_trylock_retry(rw);
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}
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static inline int _raw_write_trylock(rwlock_t *rw)
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{
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if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
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return 1;
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return _raw_write_trylock_retry(rw);
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}
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#endif /* __ASM_SPINLOCK_H */
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