From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- arch/arc/include/asm/spinlock.h | 382 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 382 insertions(+) create mode 100644 arch/arc/include/asm/spinlock.h (limited to 'arch/arc/include/asm/spinlock.h') diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h new file mode 100644 index 0000000000..1928716089 --- /dev/null +++ b/arch/arc/include/asm/spinlock.h @@ -0,0 +1,382 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) + */ + +#ifndef __ASM_SPINLOCK_H +#define __ASM_SPINLOCK_H + +#include +#include +#include + +#define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__) + +#ifdef CONFIG_ARC_HAS_LLSC + +static inline void arch_spin_lock(arch_spinlock_t *lock) +{ + unsigned int val; + + __asm__ __volatile__( + "1: llock %[val], [%[slock]] \n" + " breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */ + " scond %[LOCKED], [%[slock]] \n" /* acquire */ + " bnz 1b \n" + " \n" + : [val] "=&r" (val) + : [slock] "r" (&(lock->slock)), + [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__) + : "memory", "cc"); + + /* + * ACQUIRE barrier to ensure load/store after taking the lock + * don't "bleed-up" out of the critical section (leak-in is allowed) + * http://www.spinics.net/lists/kernel/msg2010409.html + * + * ARCv2 only has load-load, store-store and all-all barrier + * thus need the full all-all barrier + */ + smp_mb(); +} + +/* 1 - lock taken successfully */ +static inline int arch_spin_trylock(arch_spinlock_t *lock) +{ + unsigned int val, got_it = 0; + + __asm__ __volatile__( + "1: llock %[val], [%[slock]] \n" + " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */ + " scond %[LOCKED], [%[slock]] \n" /* acquire */ + " bnz 1b \n" + " mov %[got_it], 1 \n" + "4: \n" + " \n" + : [val] "=&r" (val), + [got_it] "+&r" (got_it) + : [slock] "r" (&(lock->slock)), + [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__) + : "memory", "cc"); + + smp_mb(); + + return got_it; +} + +static inline void arch_spin_unlock(arch_spinlock_t *lock) +{ + smp_mb(); + + WRITE_ONCE(lock->slock, __ARCH_SPIN_LOCK_UNLOCKED__); +} + +/* + * Read-write spinlocks, allowing multiple readers but only one writer. + * Unfair locking as Writers could be starved indefinitely by Reader(s) + */ + +static inline void arch_read_lock(arch_rwlock_t *rw) +{ + unsigned int val; + + /* + * zero means writer holds the lock exclusively, deny Reader. + * Otherwise grant lock to first/subseq reader + * + * if (rw->counter > 0) { + * rw->counter--; + * ret = 1; + * } + */ + + __asm__ __volatile__( + "1: llock %[val], [%[rwlock]] \n" + " brls %[val], %[WR_LOCKED], 1b\n" /* <= 0: spin while write locked */ + " sub %[val], %[val], 1 \n" /* reader lock */ + " scond %[val], [%[rwlock]] \n" + " bnz 1b \n" + " \n" + : [val] "=&r" (val) + : [rwlock] "r" (&(rw->counter)), + [WR_LOCKED] "ir" (0) + : "memory", "cc"); + + smp_mb(); +} + +/* 1 - lock taken successfully */ +static inline int arch_read_trylock(arch_rwlock_t *rw) +{ + unsigned int val, got_it = 0; + + __asm__ __volatile__( + "1: llock %[val], [%[rwlock]] \n" + " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */ + " sub %[val], %[val], 1 \n" /* counter-- */ + " scond %[val], [%[rwlock]] \n" + " bnz 1b \n" /* retry if collided with someone */ + " mov %[got_it], 1 \n" + " \n" + "4: ; --- done --- \n" + + : [val] "=&r" (val), + [got_it] "+&r" (got_it) + : [rwlock] "r" (&(rw->counter)), + [WR_LOCKED] "ir" (0) + : "memory", "cc"); + + smp_mb(); + + return got_it; +} + +static inline void arch_write_lock(arch_rwlock_t *rw) +{ + unsigned int val; + + /* + * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__), + * deny writer. Otherwise if unlocked grant to writer + * Hence the claim that Linux rwlocks are unfair to writers. + * (can be starved for an indefinite time by readers). + * + * if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) { + * rw->counter = 0; + * ret = 1; + * } + */ + + __asm__ __volatile__( + "1: llock %[val], [%[rwlock]] \n" + " brne %[val], %[UNLOCKED], 1b \n" /* while !UNLOCKED spin */ + " mov %[val], %[WR_LOCKED] \n" + " scond %[val], [%[rwlock]] \n" + " bnz 1b \n" + " \n" + : [val] "=&r" (val) + : [rwlock] "r" (&(rw->counter)), + [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__), + [WR_LOCKED] "ir" (0) + : "memory", "cc"); + + smp_mb(); +} + +/* 1 - lock taken successfully */ +static inline int arch_write_trylock(arch_rwlock_t *rw) +{ + unsigned int val, got_it = 0; + + __asm__ __volatile__( + "1: llock %[val], [%[rwlock]] \n" + " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */ + " mov %[val], %[WR_LOCKED] \n" + " scond %[val], [%[rwlock]] \n" + " bnz 1b \n" /* retry if collided with someone */ + " mov %[got_it], 1 \n" + " \n" + "4: ; --- done --- \n" + + : [val] "=&r" (val), + [got_it] "+&r" (got_it) + : [rwlock] "r" (&(rw->counter)), + [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__), + [WR_LOCKED] "ir" (0) + : "memory", "cc"); + + smp_mb(); + + return got_it; +} + +static inline void arch_read_unlock(arch_rwlock_t *rw) +{ + unsigned int val; + + smp_mb(); + + /* + * rw->counter++; + */ + __asm__ __volatile__( + "1: llock %[val], [%[rwlock]] \n" + " add %[val], %[val], 1 \n" + " scond %[val], [%[rwlock]] \n" + " bnz 1b \n" + " \n" + : [val] "=&r" (val) + : [rwlock] "r" (&(rw->counter)) + : "memory", "cc"); +} + +static inline void arch_write_unlock(arch_rwlock_t *rw) +{ + smp_mb(); + + WRITE_ONCE(rw->counter, __ARCH_RW_LOCK_UNLOCKED__); +} + +#else /* !CONFIG_ARC_HAS_LLSC */ + +static inline void arch_spin_lock(arch_spinlock_t *lock) +{ + unsigned int val = __ARCH_SPIN_LOCK_LOCKED__; + + /* + * Per lkmm, smp_mb() is only required after _lock (and before_unlock) + * for ACQ and REL semantics respectively. However EX based spinlocks + * need the extra smp_mb to workaround a hardware quirk. + */ + smp_mb(); + + __asm__ __volatile__( + "1: ex %0, [%1] \n" + " breq %0, %2, 1b \n" + : "+&r" (val) + : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__) + : "memory"); + + smp_mb(); +} + +/* 1 - lock taken successfully */ +static inline int arch_spin_trylock(arch_spinlock_t *lock) +{ + unsigned int val = __ARCH_SPIN_LOCK_LOCKED__; + + smp_mb(); + + __asm__ __volatile__( + "1: ex %0, [%1] \n" + : "+r" (val) + : "r"(&(lock->slock)) + : "memory"); + + smp_mb(); + + return (val == __ARCH_SPIN_LOCK_UNLOCKED__); +} + +static inline void arch_spin_unlock(arch_spinlock_t *lock) +{ + unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__; + + /* + * RELEASE barrier: given the instructions avail on ARCv2, full barrier + * is the only option + */ + smp_mb(); + + /* + * EX is not really required here, a simple STore of 0 suffices. + * However this causes tasklist livelocks in SystemC based SMP virtual + * platforms where the systemc core scheduler uses EX as a cue for + * moving to next core. Do a git log of this file for details + */ + __asm__ __volatile__( + " ex %0, [%1] \n" + : "+r" (val) + : "r"(&(lock->slock)) + : "memory"); + + /* + * see pairing version/comment in arch_spin_lock above + */ + smp_mb(); +} + +/* + * Read-write spinlocks, allowing multiple readers but only one writer. + * Unfair locking as Writers could be starved indefinitely by Reader(s) + * + * The spinlock itself is contained in @counter and access to it is + * serialized with @lock_mutex. + */ + +/* 1 - lock taken successfully */ +static inline int arch_read_trylock(arch_rwlock_t *rw) +{ + int ret = 0; + unsigned long flags; + + local_irq_save(flags); + arch_spin_lock(&(rw->lock_mutex)); + + /* + * zero means writer holds the lock exclusively, deny Reader. + * Otherwise grant lock to first/subseq reader + */ + if (rw->counter > 0) { + rw->counter--; + ret = 1; + } + + arch_spin_unlock(&(rw->lock_mutex)); + local_irq_restore(flags); + + return ret; +} + +/* 1 - lock taken successfully */ +static inline int arch_write_trylock(arch_rwlock_t *rw) +{ + int ret = 0; + unsigned long flags; + + local_irq_save(flags); + arch_spin_lock(&(rw->lock_mutex)); + + /* + * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__), + * deny writer. Otherwise if unlocked grant to writer + * Hence the claim that Linux rwlocks are unfair to writers. + * (can be starved for an indefinite time by readers). + */ + if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) { + rw->counter = 0; + ret = 1; + } + arch_spin_unlock(&(rw->lock_mutex)); + local_irq_restore(flags); + + return ret; +} + +static inline void arch_read_lock(arch_rwlock_t *rw) +{ + while (!arch_read_trylock(rw)) + cpu_relax(); +} + +static inline void arch_write_lock(arch_rwlock_t *rw) +{ + while (!arch_write_trylock(rw)) + cpu_relax(); +} + +static inline void arch_read_unlock(arch_rwlock_t *rw) +{ + unsigned long flags; + + local_irq_save(flags); + arch_spin_lock(&(rw->lock_mutex)); + rw->counter++; + arch_spin_unlock(&(rw->lock_mutex)); + local_irq_restore(flags); +} + +static inline void arch_write_unlock(arch_rwlock_t *rw) +{ + unsigned long flags; + + local_irq_save(flags); + arch_spin_lock(&(rw->lock_mutex)); + rw->counter = __ARCH_RW_LOCK_UNLOCKED__; + arch_spin_unlock(&(rw->lock_mutex)); + local_irq_restore(flags); +} + +#endif + +#endif /* __ASM_SPINLOCK_H */ -- cgit v1.2.3