383 lines
8.4 KiB
C
383 lines
8.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*/
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#ifndef __ASM_SPINLOCK_H
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#define __ASM_SPINLOCK_H
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#include <asm/spinlock_types.h>
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#include <asm/processor.h>
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#include <asm/barrier.h>
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#define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
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#ifdef CONFIG_ARC_HAS_LLSC
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static inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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unsigned int val;
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__asm__ __volatile__(
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"1: llock %[val], [%[slock]] \n"
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" breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */
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" scond %[LOCKED], [%[slock]] \n" /* acquire */
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" bnz 1b \n"
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" \n"
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: [val] "=&r" (val)
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: [slock] "r" (&(lock->slock)),
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[LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
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: "memory", "cc");
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/*
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* ACQUIRE barrier to ensure load/store after taking the lock
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* don't "bleed-up" out of the critical section (leak-in is allowed)
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* http://www.spinics.net/lists/kernel/msg2010409.html
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*
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* ARCv2 only has load-load, store-store and all-all barrier
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* thus need the full all-all barrier
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*/
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smp_mb();
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}
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/* 1 - lock taken successfully */
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static inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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unsigned int val, got_it = 0;
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__asm__ __volatile__(
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"1: llock %[val], [%[slock]] \n"
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" breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */
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" scond %[LOCKED], [%[slock]] \n" /* acquire */
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" bnz 1b \n"
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" mov %[got_it], 1 \n"
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"4: \n"
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" \n"
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: [val] "=&r" (val),
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[got_it] "+&r" (got_it)
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: [slock] "r" (&(lock->slock)),
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[LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
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: "memory", "cc");
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smp_mb();
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return got_it;
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}
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static inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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smp_mb();
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WRITE_ONCE(lock->slock, __ARCH_SPIN_LOCK_UNLOCKED__);
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}
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/*
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* Read-write spinlocks, allowing multiple readers but only one writer.
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* Unfair locking as Writers could be starved indefinitely by Reader(s)
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*/
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static inline void arch_read_lock(arch_rwlock_t *rw)
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{
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unsigned int val;
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/*
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* zero means writer holds the lock exclusively, deny Reader.
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* Otherwise grant lock to first/subseq reader
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*
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* if (rw->counter > 0) {
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* rw->counter--;
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* ret = 1;
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* }
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*/
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__asm__ __volatile__(
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"1: llock %[val], [%[rwlock]] \n"
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" brls %[val], %[WR_LOCKED], 1b\n" /* <= 0: spin while write locked */
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" sub %[val], %[val], 1 \n" /* reader lock */
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" scond %[val], [%[rwlock]] \n"
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" bnz 1b \n"
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" \n"
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: [val] "=&r" (val)
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: [rwlock] "r" (&(rw->counter)),
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[WR_LOCKED] "ir" (0)
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: "memory", "cc");
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smp_mb();
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}
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/* 1 - lock taken successfully */
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static inline int arch_read_trylock(arch_rwlock_t *rw)
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{
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unsigned int val, got_it = 0;
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__asm__ __volatile__(
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"1: llock %[val], [%[rwlock]] \n"
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" brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */
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" sub %[val], %[val], 1 \n" /* counter-- */
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" scond %[val], [%[rwlock]] \n"
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" bnz 1b \n" /* retry if collided with someone */
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" mov %[got_it], 1 \n"
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" \n"
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"4: ; --- done --- \n"
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: [val] "=&r" (val),
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[got_it] "+&r" (got_it)
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: [rwlock] "r" (&(rw->counter)),
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[WR_LOCKED] "ir" (0)
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: "memory", "cc");
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smp_mb();
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return got_it;
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}
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static inline void arch_write_lock(arch_rwlock_t *rw)
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{
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unsigned int val;
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/*
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* If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
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* deny writer. Otherwise if unlocked grant to writer
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* Hence the claim that Linux rwlocks are unfair to writers.
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* (can be starved for an indefinite time by readers).
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*
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* if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
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* rw->counter = 0;
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* ret = 1;
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* }
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*/
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__asm__ __volatile__(
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"1: llock %[val], [%[rwlock]] \n"
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" brne %[val], %[UNLOCKED], 1b \n" /* while !UNLOCKED spin */
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" mov %[val], %[WR_LOCKED] \n"
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" scond %[val], [%[rwlock]] \n"
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" bnz 1b \n"
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" \n"
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: [val] "=&r" (val)
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: [rwlock] "r" (&(rw->counter)),
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[UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
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[WR_LOCKED] "ir" (0)
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: "memory", "cc");
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smp_mb();
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}
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/* 1 - lock taken successfully */
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static inline int arch_write_trylock(arch_rwlock_t *rw)
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{
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unsigned int val, got_it = 0;
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__asm__ __volatile__(
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"1: llock %[val], [%[rwlock]] \n"
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" brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */
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" mov %[val], %[WR_LOCKED] \n"
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" scond %[val], [%[rwlock]] \n"
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" bnz 1b \n" /* retry if collided with someone */
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" mov %[got_it], 1 \n"
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" \n"
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"4: ; --- done --- \n"
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: [val] "=&r" (val),
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[got_it] "+&r" (got_it)
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: [rwlock] "r" (&(rw->counter)),
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[UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
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[WR_LOCKED] "ir" (0)
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: "memory", "cc");
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smp_mb();
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return got_it;
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}
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static inline void arch_read_unlock(arch_rwlock_t *rw)
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{
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unsigned int val;
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smp_mb();
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/*
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* rw->counter++;
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*/
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__asm__ __volatile__(
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"1: llock %[val], [%[rwlock]] \n"
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" add %[val], %[val], 1 \n"
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" scond %[val], [%[rwlock]] \n"
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" bnz 1b \n"
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" \n"
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: [val] "=&r" (val)
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: [rwlock] "r" (&(rw->counter))
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: "memory", "cc");
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}
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static inline void arch_write_unlock(arch_rwlock_t *rw)
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{
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smp_mb();
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WRITE_ONCE(rw->counter, __ARCH_RW_LOCK_UNLOCKED__);
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}
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#else /* !CONFIG_ARC_HAS_LLSC */
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static inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
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/*
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* Per lkmm, smp_mb() is only required after _lock (and before_unlock)
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* for ACQ and REL semantics respectively. However EX based spinlocks
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* need the extra smp_mb to workaround a hardware quirk.
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*/
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smp_mb();
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__asm__ __volatile__(
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"1: ex %0, [%1] \n"
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" breq %0, %2, 1b \n"
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: "+&r" (val)
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: "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
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: "memory");
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smp_mb();
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}
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/* 1 - lock taken successfully */
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static inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
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smp_mb();
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__asm__ __volatile__(
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"1: ex %0, [%1] \n"
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: "+r" (val)
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: "r"(&(lock->slock))
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: "memory");
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smp_mb();
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return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
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}
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static inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;
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/*
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* RELEASE barrier: given the instructions avail on ARCv2, full barrier
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* is the only option
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*/
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smp_mb();
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/*
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* EX is not really required here, a simple STore of 0 suffices.
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* However this causes tasklist livelocks in SystemC based SMP virtual
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* platforms where the systemc core scheduler uses EX as a cue for
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* moving to next core. Do a git log of this file for details
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*/
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__asm__ __volatile__(
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" ex %0, [%1] \n"
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: "+r" (val)
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: "r"(&(lock->slock))
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: "memory");
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/*
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* see pairing version/comment in arch_spin_lock above
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*/
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smp_mb();
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}
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/*
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* Read-write spinlocks, allowing multiple readers but only one writer.
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* Unfair locking as Writers could be starved indefinitely by Reader(s)
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*
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* The spinlock itself is contained in @counter and access to it is
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* serialized with @lock_mutex.
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*/
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/* 1 - lock taken successfully */
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static inline int arch_read_trylock(arch_rwlock_t *rw)
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{
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int ret = 0;
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unsigned long flags;
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local_irq_save(flags);
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arch_spin_lock(&(rw->lock_mutex));
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/*
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* zero means writer holds the lock exclusively, deny Reader.
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* Otherwise grant lock to first/subseq reader
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*/
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if (rw->counter > 0) {
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rw->counter--;
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ret = 1;
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}
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arch_spin_unlock(&(rw->lock_mutex));
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local_irq_restore(flags);
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return ret;
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}
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/* 1 - lock taken successfully */
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static inline int arch_write_trylock(arch_rwlock_t *rw)
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{
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int ret = 0;
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unsigned long flags;
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local_irq_save(flags);
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arch_spin_lock(&(rw->lock_mutex));
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/*
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* If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
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* deny writer. Otherwise if unlocked grant to writer
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* Hence the claim that Linux rwlocks are unfair to writers.
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* (can be starved for an indefinite time by readers).
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*/
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if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
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rw->counter = 0;
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ret = 1;
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}
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arch_spin_unlock(&(rw->lock_mutex));
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local_irq_restore(flags);
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return ret;
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}
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static inline void arch_read_lock(arch_rwlock_t *rw)
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{
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while (!arch_read_trylock(rw))
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cpu_relax();
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}
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static inline void arch_write_lock(arch_rwlock_t *rw)
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{
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while (!arch_write_trylock(rw))
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cpu_relax();
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}
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static inline void arch_read_unlock(arch_rwlock_t *rw)
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{
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unsigned long flags;
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local_irq_save(flags);
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arch_spin_lock(&(rw->lock_mutex));
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rw->counter++;
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arch_spin_unlock(&(rw->lock_mutex));
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local_irq_restore(flags);
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}
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static inline void arch_write_unlock(arch_rwlock_t *rw)
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{
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unsigned long flags;
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local_irq_save(flags);
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arch_spin_lock(&(rw->lock_mutex));
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rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
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arch_spin_unlock(&(rw->lock_mutex));
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local_irq_restore(flags);
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}
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#endif
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#endif /* __ASM_SPINLOCK_H */
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