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MCS: fix ARM64 issue by using smp_XXX() functions (i.e., barrier()s)

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Change-Id: I41470c082308c7c1ac91f88db2229958398d2e68
This commit is contained in:
Balazs Gerofi
2019-04-10 20:26:13 +09:00
parent ad3ee26d36
commit bdccbf7356
2 changed files with 33 additions and 17 deletions
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8
arch/x86_64/kernel/include/arch/cpu.h
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@ -42,4 +42,12 @@ static inline unsigned long read_tsc(void)
___p1; \ ___p1; \
}) })
#define smp_store_release(p, v) \
({ \
compiletime_assert_atomic_type(*p); \
barrier(); \
WRITE_ONCE(*p, v); \
})
#endif /* ARCH_CPU_H */ #endif /* ARCH_CPU_H */

42
lib/include/ihk/lock.h
View File

@ -46,6 +46,7 @@ static void mcs_lock_init(struct mcs_lock_node *node)
#endif // SPIN_LOCK_IN_MCS #endif // SPIN_LOCK_IN_MCS
} }
static void __mcs_lock_lock(struct mcs_lock_node *lock, static void __mcs_lock_lock(struct mcs_lock_node *lock,
struct mcs_lock_node *node) struct mcs_lock_node *node)
{ {
@ -56,15 +57,20 @@ static void __mcs_lock_lock(struct mcs_lock_node *lock,
node->next = NULL; node->next = NULL;
node->locked = 0; node->locked = 0;
__atomic_exchange(&(lock->next), &node, &pred, __ATOMIC_SEQ_CST);
if (pred) { pred = xchg(&lock->next, node);
node->locked = 1; if (likely(pred == NULL)) {
pred->next = node; /*
while (node->locked != 0) { * Lock acquired, don't need to set node->locked to 1. Threads
cpu_pause(); * only spin on its own node->locked value for lock acquisition.
} */
return;
} }
WRITE_ONCE(pred->next, node);
/* Wait until the lock holder passes the lock down. */
while (!(smp_load_acquire(&node->locked)))
cpu_pause();
#endif // SPIN_LOCK_IN_MCS #endif // SPIN_LOCK_IN_MCS
} }
@ -74,20 +80,22 @@ static void __mcs_lock_unlock(struct mcs_lock_node *lock,
#ifdef SPIN_LOCK_IN_MCS #ifdef SPIN_LOCK_IN_MCS
ihk_mc_spinlock_unlock_noirq(&lock->spinlock); ihk_mc_spinlock_unlock_noirq(&lock->spinlock);
#else #else
if (node->next == NULL) { struct mcs_lock_node *next = READ_ONCE(node->next);
struct mcs_lock_node *desired = NULL;
struct mcs_lock_node *expected = node;
if (__atomic_compare_exchange(&(lock->next), &expected, &desired, 0,
__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
return;
}
while (node->next == NULL) { if (likely(!next)) {
/*
* Release the lock by setting it to NULL
*/
if (likely(cmpxchg(&lock->next, node, NULL) == node))
return;
/* Wait until the next pointer is set */
while (!(next = READ_ONCE(node->next)))
cpu_pause(); cpu_pause();
}
} }
node->next->locked = 0; /* Pass lock to next waiter. */
smp_store_release((&next->locked), 1);
#endif // SPIN_LOCK_IN_MCS #endif // SPIN_LOCK_IN_MCS
} }