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Diffstat (limited to 'arch/arc/include/asm/spinlock.h')
-rw-r--r--arch/arc/include/asm/spinlock.h49
1 files changed, 14 insertions, 35 deletions
diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h
index 2ba04a7db621..daa914da7968 100644
--- a/arch/arc/include/asm/spinlock.h
+++ b/arch/arc/include/asm/spinlock.h
@@ -21,8 +21,6 @@ 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 */
@@ -34,6 +32,14 @@ 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();
}
@@ -42,8 +48,6 @@ 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 */
@@ -67,9 +71,7 @@ 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__);
}
/*
@@ -81,8 +83,6 @@ 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
@@ -113,8 +113,6 @@ 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 */
@@ -140,8 +138,6 @@ 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
@@ -175,8 +171,6 @@ 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 */
@@ -217,17 +211,13 @@ 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 */
@@ -237,10 +227,9 @@ 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 +246,6 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
#endif
: "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();
}
@@ -309,8 +290,7 @@ 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();
}
@@ -344,7 +324,6 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
arch_spin_unlock(&(rw->lock_mutex));
local_irq_restore(flags);
- smp_mb();
return ret;
}