Changes since v3.14.2-rt2

    - rwsem readers are now not allowed to nest. A patch rom Steven Rostedt.
    - a few bugs were fixed in the hotplug code which were made during the
      v3.14 port. Fixed by Mike Galbraith.
    - Mike Galbraith sent a patch which might fix lazy preempt on x86_64.
      Patch applied and my machine still explodes therefore lazy preempt
      remains off on x86_64.
    - Mike Galbraith sent a few patches to get cpu hoplug to work. This
      includes lg_global_trylock_relax().
    - A few push downs of migrate_disable() (where we call migrate_disable()
      after the rt_mutex_trylock()) have been reverted. It seems hotplug is
      not too happy about this. A patch by Steven Rostedt and and Mike
      Galbraith
    - There was a complaint about a backrace from run_local_timers() in UP
      mode because a spin_try_lock() failed. _This_ particular case was not
      an error. This optimization was for FULL_NO_HZ which is pointless on
      UP because there is no spare CPU. Therefore, this optimization is
      disabled in UP mode and the backtrace is gone. Reported by Stanislav
      Meduna.
    - block-mq notifier uses now a spinlock and runs during CPU_POST_DEAD
      instead at CPU_DEAD time. lockdep complained about the sleeping
      ctx->lock within the rawlock (blk_mq_cpu_notify_lock) and CPU_DEAD
      runs with irqs off.

    Known issues:

          - bcache is disabled.

          - lazy preempt on x86_64 leads to a crash with some load.

          - CPU hotplug works in general. Steven's test script however
            deadlocks usually on the second invocation.

Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 25afbcc3a742..5fb26f785320 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -48,9 +48,14 @@ static struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
 	return __blk_mq_get_ctx(q, get_cpu_light());
 }
 
-static void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
+static void __blk_mq_put_ctx(struct blk_mq_ctx *ctx)
 {
 	spin_unlock(&ctx->cpu_lock);
+}
+
+static void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
+{
+	__blk_mq_put_ctx(ctx);
 	put_cpu_light();
 }
 
@@ -980,6 +985,7 @@ static void blk_mq_hctx_notify(void *data, unsigned long action,
 		clear_bit(ctx->index_hw, hctx->ctx_map);
 	}
 	spin_unlock(&ctx->lock);
+	__blk_mq_put_ctx(ctx);
 
 	if (list_empty(&tmp))
 		return;