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Diffstat (limited to 'arch/arc/include/asm/spinlock.h')
-rw-r--r--arch/arc/include/asm/spinlock.h294
1 files changed, 266 insertions, 28 deletions
diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h
index f158197ac5b0..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
@@ -14,61 +11,296 @@
#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)
-#define arch_spin_unlock_wait(x) \
- do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0)
+
+#ifdef CONFIG_ARC_HAS_LLSC
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
- unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
+ 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" (tmp)
+ : "+&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 tmp = __ARCH_SPIN_LOCK_LOCKED__;
+ unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
+
+ smp_mb();
__asm__ __volatile__(
"1: ex %0, [%1] \n"
- : "+r" (tmp)
+ : "+r" (val)
: "r"(&(lock->slock))
: "memory");
- return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__);
+ smp_mb();
+
+ return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
}
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
- lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;
+ 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.
- *
- * Unfair locking as Writers could be starved indefinitely by Reader(s)
*/
-/* Would read_trylock() succeed? */
-#define arch_read_can_lock(x) ((x)->counter > 0)
-
-/* Would write_trylock() succeed? */
-#define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
-
/* 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));
/*
@@ -81,8 +313,8 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
}
arch_spin_unlock(&(rw->lock_mutex));
+ local_irq_restore(flags);
- smp_mb();
return ret;
}
@@ -90,7 +322,9 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
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));
/*
@@ -104,6 +338,7 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
ret = 1;
}
arch_spin_unlock(&(rw->lock_mutex));
+ local_irq_restore(flags);
return ret;
}
@@ -122,23 +357,26 @@ static inline void arch_write_lock(arch_rwlock_t *rw)
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);
}
-#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
#endif /* __ASM_SPINLOCK_H */
generated by cgit (git 2.34.1) at 2025-12-25 08:24:26 +0000