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202fb4ef81
If the spinlock "next" ticket wraps around between the initial LDR and the cmpxchg in the LSE version of spin_trylock, then we can erroneously think that we have successfuly acquired the lock because we only check whether the next ticket return by the cmpxchg is equal to the owner ticket in our updated lock word. This patch fixes the issue by performing a full 32-bit check of the lock word when trying to determine whether or not the CASA instruction updated memory. Reported-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
146 lines
3.3 KiB
C
146 lines
3.3 KiB
C
/*
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* Copyright (C) 2012 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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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/lse.h>
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#include <asm/spinlock_types.h>
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#include <asm/processor.h>
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/*
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* Spinlock implementation.
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*
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* The memory barriers are implicit with the load-acquire and store-release
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* instructions.
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*/
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static inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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unsigned int tmp;
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arch_spinlock_t lockval, newval;
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asm volatile(
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/* Atomically increment the next ticket. */
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ARM64_LSE_ATOMIC_INSN(
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/* LL/SC */
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" prfm pstl1strm, %3\n"
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"1: ldaxr %w0, %3\n"
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" add %w1, %w0, %w5\n"
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" stxr %w2, %w1, %3\n"
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" cbnz %w2, 1b\n",
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/* LSE atomics */
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" mov %w2, %w5\n"
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" ldadda %w2, %w0, %3\n"
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__nops(3)
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)
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/* Did we get the lock? */
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" eor %w1, %w0, %w0, ror #16\n"
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" cbz %w1, 3f\n"
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/*
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* No: spin on the owner. Send a local event to avoid missing an
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* unlock before the exclusive load.
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*/
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" sevl\n"
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"2: wfe\n"
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" ldaxrh %w2, %4\n"
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" eor %w1, %w2, %w0, lsr #16\n"
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" cbnz %w1, 2b\n"
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/* We got the lock. Critical section starts here. */
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"3:"
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: "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock)
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: "Q" (lock->owner), "I" (1 << TICKET_SHIFT)
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: "memory");
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}
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static inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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unsigned int tmp;
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arch_spinlock_t lockval;
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asm volatile(ARM64_LSE_ATOMIC_INSN(
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/* LL/SC */
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" prfm pstl1strm, %2\n"
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"1: ldaxr %w0, %2\n"
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" eor %w1, %w0, %w0, ror #16\n"
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" cbnz %w1, 2f\n"
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" add %w0, %w0, %3\n"
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" stxr %w1, %w0, %2\n"
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" cbnz %w1, 1b\n"
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"2:",
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/* LSE atomics */
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" ldr %w0, %2\n"
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" eor %w1, %w0, %w0, ror #16\n"
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" cbnz %w1, 1f\n"
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" add %w1, %w0, %3\n"
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" casa %w0, %w1, %2\n"
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" sub %w1, %w1, %3\n"
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" eor %w1, %w1, %w0\n"
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"1:")
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: "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
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: "I" (1 << TICKET_SHIFT)
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: "memory");
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return !tmp;
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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 long tmp;
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asm volatile(ARM64_LSE_ATOMIC_INSN(
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/* LL/SC */
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" ldrh %w1, %0\n"
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" add %w1, %w1, #1\n"
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" stlrh %w1, %0",
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/* LSE atomics */
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" mov %w1, #1\n"
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" staddlh %w1, %0\n"
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__nops(1))
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: "=Q" (lock->owner), "=&r" (tmp)
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:
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: "memory");
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}
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static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
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{
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return lock.owner == lock.next;
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}
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static inline int arch_spin_is_locked(arch_spinlock_t *lock)
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{
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/*
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* Ensure prior spin_lock operations to other locks have completed
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* on this CPU before we test whether "lock" is locked.
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*/
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smp_mb(); /* ^^^ */
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return !arch_spin_value_unlocked(READ_ONCE(*lock));
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}
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static inline int arch_spin_is_contended(arch_spinlock_t *lock)
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{
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arch_spinlock_t lockval = READ_ONCE(*lock);
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return (lockval.next - lockval.owner) > 1;
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}
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#define arch_spin_is_contended arch_spin_is_contended
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#include <asm/qrwlock.h>
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/* See include/linux/spinlock.h */
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#define smp_mb__after_spinlock() smp_mb()
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#endif /* __ASM_SPINLOCK_H */
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