diff --git a/arch/powerpc/lib/qspinlock.c b/arch/powerpc/lib/qspinlock.c index 18e21574e6c5..41afd8e68918 100644 --- a/arch/powerpc/lib/qspinlock.c +++ b/arch/powerpc/lib/qspinlock.c @@ -26,6 +26,7 @@ static bool maybe_stealers __read_mostly = true; static int head_spins __read_mostly = (1 << 8); static bool pv_yield_owner __read_mostly = true; +static bool pv_yield_prev __read_mostly = true; static DEFINE_PER_CPU_ALIGNED(struct qnodes, qnodes); @@ -195,6 +196,32 @@ relax: cpu_relax(); } +static __always_inline void yield_to_prev(struct qspinlock *lock, struct qnode *node, u32 val, bool paravirt) +{ + int prev_cpu = decode_tail_cpu(val); + u32 yield_count; + + if (!paravirt) + goto relax; + + if (!pv_yield_prev) + goto relax; + + yield_count = yield_count_of(prev_cpu); + if ((yield_count & 1) == 0) + goto relax; /* owner vcpu is running */ + + smp_rmb(); /* See yield_to_locked_owner comment */ + + if (!node->locked) { + yield_to_preempted(prev_cpu, yield_count); + return; + } + +relax: + cpu_relax(); +} + static __always_inline bool try_to_steal_lock(struct qspinlock *lock, bool paravirt) { @@ -269,7 +296,7 @@ static __always_inline void queued_spin_lock_mcs_queue(struct qspinlock *lock, b /* Wait for mcs node lock to be released */ while (!node->locked) - cpu_relax(); + yield_to_prev(lock, node, old, paravirt); smp_rmb(); /* acquire barrier for the mcs lock */ } @@ -417,12 +444,29 @@ static int pv_yield_owner_get(void *data, u64 *val) DEFINE_SIMPLE_ATTRIBUTE(fops_pv_yield_owner, pv_yield_owner_get, pv_yield_owner_set, "%llu\n"); +static int pv_yield_prev_set(void *data, u64 val) +{ + pv_yield_prev = !!val; + + return 0; +} + +static int pv_yield_prev_get(void *data, u64 *val) +{ + *val = pv_yield_prev; + + return 0; +} + +DEFINE_SIMPLE_ATTRIBUTE(fops_pv_yield_prev, pv_yield_prev_get, pv_yield_prev_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); if (is_shared_processor()) { debugfs_create_file("qspl_pv_yield_owner", 0600, arch_debugfs_dir, NULL, &fops_pv_yield_owner); + debugfs_create_file("qspl_pv_yield_prev", 0600, arch_debugfs_dir, NULL, &fops_pv_yield_prev); } return 0;