blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe

[firefly-linux-kernel-4.4.55.git] / lib / percpu-refcount.c

diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index fe5a3342e9607d8ee9bd11678ef31d070a81ccf5..a89cf09a82684d729222699afb1f911162977ba7 100644 (file)
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -184,3 +184,19 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
        call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);
 }
 EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm);
+
+/*
+ * XXX: Temporary kludge to work around SCSI blk-mq stall.  Used only by
+ * block/blk-mq.c::blk_mq_freeze_queue().  Will be removed during v3.18
+ * devel cycle.  Do not use anywhere else.
+ */
+void __percpu_ref_kill_expedited(struct percpu_ref *ref)
+{
+       WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,
+                 "percpu_ref_kill() called more than once on %pf!",
+                 ref->release);
+
+       ref->pcpu_count_ptr |= PCPU_REF_DEAD;
+       synchronize_sched_expedited();
+       percpu_ref_kill_rcu(&ref->rcu);
+}