ALSA: seq: Fix potential concurrent access to the deleted pool

[linux-2.6-block.git] / sound / core / seq / seq_fifo.c

diff --git a/sound/core/seq/seq_fifo.c b/sound/core/seq/seq_fifo.c
index ea69261f269aa4be262cffe736d876c6136b2d78..eaaa8b5830bb6471616c2c4e0458ab469e6c4c85 100644 (file)
--- a/sound/core/seq/seq_fifo.c
+++ b/sound/core/seq/seq_fifo.c
@@ -263,3 +263,20 @@ int snd_seq_fifo_resize(struct snd_seq_fifo *f, int poolsize)
 
        return 0;
 }
+
+/* get the number of unused cells safely */
+int snd_seq_fifo_unused_cells(struct snd_seq_fifo *f)
+{
+       unsigned long flags;
+       int cells;
+
+       if (!f)
+               return 0;
+
+       snd_use_lock_use(&f->use_lock);
+       spin_lock_irqsave(&f->lock, flags);
+       cells = snd_seq_unused_cells(f->pool);
+       spin_unlock_irqrestore(&f->lock, flags);
+       snd_use_lock_free(&f->use_lock);
+       return cells;
+}