diff options
Diffstat (limited to 'kernel/locking')
| -rw-r--r-- | kernel/locking/qspinlock.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 5fc8c311b8fe..ee7deb08d43d 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -90,7 +90,7 @@ static DEFINE_PER_CPU_ALIGNED(struct mcs_spinlock, mcs_nodes[MAX_NODES]); * therefore increment the cpu number by one. */ -static inline u32 encode_tail(int cpu, int idx) +static inline __pure u32 encode_tail(int cpu, int idx) { u32 tail; @@ -103,7 +103,7 @@ static inline u32 encode_tail(int cpu, int idx) return tail; } -static inline struct mcs_spinlock *decode_tail(u32 tail) +static inline __pure struct mcs_spinlock *decode_tail(u32 tail) { int cpu = (tail >> _Q_TAIL_CPU_OFFSET) - 1; int idx = (tail & _Q_TAIL_IDX_MASK) >> _Q_TAIL_IDX_OFFSET; @@ -455,6 +455,8 @@ queue: * pending stuff. * * p,*,* -> n,*,* + * + * RELEASE, such that the stores to @node must be complete. */ old = xchg_tail(lock, tail); next = NULL; @@ -465,6 +467,15 @@ queue: */ if (old & _Q_TAIL_MASK) { prev = decode_tail(old); + /* + * The above xchg_tail() is also a load of @lock which generates, + * through decode_tail(), a pointer. + * + * The address dependency matches the RELEASE of xchg_tail() + * such that the access to @prev must happen after. + */ + smp_read_barrier_depends(); + WRITE_ONCE(prev->next, node); pv_wait_node(node, prev); |