diff options
Diffstat (limited to 'arch/arc/include/asm/spinlock.h')
| -rw-r--r-- | arch/arc/include/asm/spinlock.h | 76 |
1 files changed, 21 insertions, 55 deletions
diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h index 233d5ffe6ec7..192871608925 100644 --- a/arch/arc/include/asm/spinlock.h +++ b/arch/arc/include/asm/spinlock.h @@ -1,9 +1,6 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ /* * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. */ #ifndef __ASM_SPINLOCK_H @@ -14,12 +11,6 @@ #include <asm/barrier.h> #define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__) -#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) - -static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) -{ - smp_cond_load_acquire(&lock->slock, !VAL); -} #ifdef CONFIG_ARC_HAS_LLSC @@ -27,8 +18,6 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) { unsigned int val; - smp_mb(); - __asm__ __volatile__( "1: llock %[val], [%[slock]] \n" " breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */ @@ -40,6 +29,14 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) [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(); } @@ -48,8 +45,6 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock) { unsigned int val, got_it = 0; - smp_mb(); - __asm__ __volatile__( "1: llock %[val], [%[slock]] \n" " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */ @@ -73,9 +68,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) { smp_mb(); - lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__; - - smp_mb(); + WRITE_ONCE(lock->slock, __ARCH_SPIN_LOCK_UNLOCKED__); } /* @@ -87,8 +80,6 @@ static inline void arch_read_lock(arch_rwlock_t *rw) { unsigned int val; - smp_mb(); - /* * zero means writer holds the lock exclusively, deny Reader. * Otherwise grant lock to first/subseq reader @@ -119,8 +110,6 @@ static inline int arch_read_trylock(arch_rwlock_t *rw) { unsigned int val, got_it = 0; - smp_mb(); - __asm__ __volatile__( "1: llock %[val], [%[rwlock]] \n" " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */ @@ -146,8 +135,6 @@ static inline void arch_write_lock(arch_rwlock_t *rw) { unsigned int val; - smp_mb(); - /* * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__), * deny writer. Otherwise if unlocked grant to writer @@ -181,8 +168,6 @@ static inline int arch_write_trylock(arch_rwlock_t *rw) { unsigned int val, got_it = 0; - smp_mb(); - __asm__ __volatile__( "1: llock %[val], [%[rwlock]] \n" " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */ @@ -223,17 +208,13 @@ static inline void arch_read_unlock(arch_rwlock_t *rw) : [val] "=&r" (val) : [rwlock] "r" (&(rw->counter)) : "memory", "cc"); - - smp_mb(); } static inline void arch_write_unlock(arch_rwlock_t *rw) { smp_mb(); - rw->counter = __ARCH_RW_LOCK_UNLOCKED__; - - smp_mb(); + WRITE_ONCE(rw->counter, __ARCH_RW_LOCK_UNLOCKED__); } #else /* !CONFIG_ARC_HAS_LLSC */ @@ -243,10 +224,9 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) unsigned int val = __ARCH_SPIN_LOCK_LOCKED__; /* - * This smp_mb() is technically superfluous, we only need the one - * after the lock for providing the ACQUIRE semantics. - * However doing the "right" thing was regressing hackbench - * so keeping this, pending further investigation + * 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(); @@ -257,14 +237,6 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__) : "memory"); - /* - * 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(); } @@ -296,6 +268,12 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) */ 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) @@ -303,8 +281,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) : "memory"); /* - * superfluous, but keeping for now - see pairing version in - * arch_spin_lock above + * see pairing version/comment in arch_spin_lock above */ smp_mb(); } @@ -338,7 +315,6 @@ static inline int arch_read_trylock(arch_rwlock_t *rw) arch_spin_unlock(&(rw->lock_mutex)); local_irq_restore(flags); - smp_mb(); return ret; } @@ -403,14 +379,4 @@ static inline void arch_write_unlock(arch_rwlock_t *rw) #endif -#define arch_read_can_lock(x) ((x)->counter > 0) -#define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__) - -#define arch_read_lock_flags(lock, flags) arch_read_lock(lock) -#define arch_write_lock_flags(lock, flags) arch_write_lock(lock) - -#define arch_spin_relax(lock) cpu_relax() -#define arch_read_relax(lock) cpu_relax() -#define arch_write_relax(lock) cpu_relax() - #endif /* __ASM_SPINLOCK_H */ |