diff options
| -rw-r--r-- | arch/powerpc/include/asm/qspinlock_types.h | 8 | ||||
| -rw-r--r-- | arch/powerpc/lib/qspinlock.c | 53 |
2 files changed, 60 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/qspinlock_types.h b/arch/powerpc/include/asm/qspinlock_types.h index b9a5a52fa670..1911a8a16237 100644 --- a/arch/powerpc/include/asm/qspinlock_types.h +++ b/arch/powerpc/include/asm/qspinlock_types.h @@ -29,7 +29,8 @@ typedef struct qspinlock { * Bitfields in the lock word: * * 0: locked bit - * 1-16: unused bits + * 1-15: unused bits + * 16: must queue bit * 17-31: tail cpu (+1) */ #define _Q_SET_MASK(type) (((1U << _Q_ ## type ## _BITS) - 1)\ @@ -39,6 +40,11 @@ typedef struct qspinlock { #define _Q_LOCKED_BITS 1 #define _Q_LOCKED_VAL (1U << _Q_LOCKED_OFFSET) +/* 0x00010000 */ +#define _Q_MUST_Q_OFFSET 16 +#define _Q_MUST_Q_BITS 1 +#define _Q_MUST_Q_VAL (1U << _Q_MUST_Q_OFFSET) + /* 0xfffe0000 */ #define _Q_TAIL_CPU_OFFSET 17 #define _Q_TAIL_CPU_BITS 15 diff --git a/arch/powerpc/lib/qspinlock.c b/arch/powerpc/lib/qspinlock.c index 6ffd3261064c..9cd442d46b9f 100644 --- a/arch/powerpc/lib/qspinlock.c +++ b/arch/powerpc/lib/qspinlock.c @@ -22,6 +22,7 @@ struct qnodes { /* Tuning parameters */ static int steal_spins __read_mostly = (1 << 5); static bool maybe_stealers __read_mostly = true; +static int head_spins __read_mostly = (1 << 8); static DEFINE_PER_CPU_ALIGNED(struct qnodes, qnodes); @@ -30,6 +31,11 @@ static __always_inline int get_steal_spins(void) return steal_spins; } +static __always_inline int get_head_spins(void) +{ + return head_spins; +} + static inline u32 encode_tail_cpu(int cpu) { return (cpu + 1) << _Q_TAIL_CPU_OFFSET; @@ -104,6 +110,22 @@ static __always_inline u32 publish_tail_cpu(struct qspinlock *lock, u32 tail) return prev; } +static __always_inline u32 set_mustq(struct qspinlock *lock) +{ + u32 prev; + + asm volatile( +"1: lwarx %0,0,%1 # set_mustq \n" +" or %0,%0,%2 \n" +" stwcx. %0,0,%1 \n" +" bne- 1b \n" + : "=&r" (prev) + : "r" (&lock->val), "r" (_Q_MUST_Q_VAL) + : "cr0", "memory"); + + return prev; +} + static struct qnode *get_tail_qnode(struct qspinlock *lock, u32 val) { int cpu = decode_tail_cpu(val); @@ -139,6 +161,9 @@ static inline bool try_to_steal_lock(struct qspinlock *lock) do { u32 val = READ_ONCE(lock->val); + if (val & _Q_MUST_Q_VAL) + break; + if (unlikely(!(val & _Q_LOCKED_VAL))) { if (__queued_spin_trylock_steal(lock)) return true; @@ -157,7 +182,9 @@ static inline void queued_spin_lock_mcs_queue(struct qspinlock *lock) struct qnodes *qnodesp; struct qnode *next, *node; u32 val, old, tail; + bool mustq = false; int idx; + int iters = 0; BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); @@ -209,6 +236,15 @@ again: break; cpu_relax(); + if (!maybe_stealers) + continue; + iters++; + + if (!mustq && iters >= get_head_spins()) { + mustq = true; + set_mustq(lock); + val |= _Q_MUST_Q_VAL; + } } /* If we're the last queued, must clean up the tail. */ @@ -293,9 +329,26 @@ static int steal_spins_get(void *data, u64 *val) DEFINE_SIMPLE_ATTRIBUTE(fops_steal_spins, steal_spins_get, steal_spins_set, "%llu\n"); +static int head_spins_set(void *data, u64 val) +{ + head_spins = val; + + return 0; +} + +static int head_spins_get(void *data, u64 *val) +{ + *val = head_spins; + + return 0; +} + +DEFINE_SIMPLE_ATTRIBUTE(fops_head_spins, head_spins_get, head_spins_set, "%llu\n"); + static __init int spinlock_debugfs_init(void) { debugfs_create_file("qspl_steal_spins", 0600, arch_debugfs_dir, NULL, &fops_steal_spins); + debugfs_create_file("qspl_head_spins", 0600, arch_debugfs_dir, NULL, &fops_head_spins); return 0; } |