diff options
Diffstat (limited to 'kernel/locking/qspinlock.c')
| -rw-r--r-- | kernel/locking/qspinlock.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 8a8c3c208c5e..0875053c4050 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -412,6 +412,21 @@ 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)) { + while (!queued_spin_trylock(lock)) + cpu_relax(); + goto release; + } + node = grab_mcs_node(node, idx); /* |