diff options
Diffstat (limited to 'kernel/locking/qspinlock.c')
| -rw-r--r-- | kernel/locking/qspinlock.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 8a8c3c208c5e..5e9247dc2515 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -124,9 +124,6 @@ static inline __pure u32 encode_tail(int cpu, int idx) { u32 tail; -#ifdef CONFIG_DEBUG_SPINLOCK - BUG_ON(idx > 3); -#endif tail = (cpu + 1) << _Q_TAIL_CPU_OFFSET; tail |= idx << _Q_TAIL_IDX_OFFSET; /* assume < 4 */ @@ -412,12 +409,28 @@ pv_queue: idx = node->count++; tail = encode_tail(smp_processor_id(), idx); + /* + * 4 nodes are allocated based on the assumption that there will + * not be nested NMIs taking spinlocks. That may not be true in + * some architectures even though the chance of needing more than + * 4 nodes will still be extremely unlikely. When that happens, + * we fall back to spinning on the lock directly without using + * any MCS node. This is not the most elegant solution, but is + * simple enough. + */ + if (unlikely(idx >= MAX_NODES)) { + qstat_inc(qstat_lock_no_node, true); + while (!queued_spin_trylock(lock)) + cpu_relax(); + goto release; + } + node = grab_mcs_node(node, idx); /* * Keep counts of non-zero index values: */ - qstat_inc(qstat_lock_idx1 + idx - 1, idx); + qstat_inc(qstat_lock_use_node2 + idx - 1, idx); /* * Ensure that we increment the head node->count before initialising |