[PATCH] IB/ehca: Reduce number of spin_lock/spin_unlocks in ehca_poll_eqs

[Anton Blanchard <anton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>]

ftrace function_graph shows ehca_poll_eqs taking and dropping a spinlock
a lot:

 16)               |          .ehca_poll_eqs() {
 16)   0.492 us    |            ._spin_lock();
 16)   0.504 us    |            ._spin_lock_irqsave();
 16)   0.502 us    |            ._spin_unlock_irqrestore();
 16)   0.490 us    |            ._spin_lock_irqsave();
 16)   0.488 us    |            ._spin_unlock_irqrestore();
 16)   0.488 us    |            ._spin_lock_irqsave();
 16)   0.488 us    |            ._spin_unlock_irqrestore();
 16)   0.490 us    |            ._spin_lock_irqsave();
 16)   0.492 us    |            ._spin_unlock_irqrestore();

Since it's all the same spinlock, we can just take and drop it once.

Signed-off-by: Anton Blanchard <anton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
---

Index: linux.trees.git/drivers/infiniband/hw/ehca/ehca_main.c
===================================================================
--- linux.trees.git.orig/drivers/infiniband/hw/ehca/ehca_main.c	2009-11-27 10:17:29.000000000 +1100
+++ linux.trees.git/drivers/infiniband/hw/ehca/ehca_main.c	2009-11-27 10:19:08.000000000 +1100
@@ -957,15 +957,17 @@ void ehca_poll_eqs(unsigned long data)
 			int max = 3;
 			volatile u64 q_ofs, q_ofs2;
 			unsigned long flags;
+
 			spin_lock_irqsave(&eq->spinlock, flags);
+
 			q_ofs = eq->ipz_queue.current_q_offset;
-			spin_unlock_irqrestore(&eq->spinlock, flags);
 			do {
-				spin_lock_irqsave(&eq->spinlock, flags);
 				q_ofs2 = eq->ipz_queue.current_q_offset;
-				spin_unlock_irqrestore(&eq->spinlock, flags);
 				max--;
 			} while (q_ofs == q_ofs2 && max > 0);
+
+			spin_unlock_irqrestore(&eq->spinlock, flags);
+
 			if (q_ofs == q_ofs2)
 				ehca_process_eq(shca, 0);
 		}
--
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