Gitweb:     http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=18c07c...
Commit:     18c07cf530cf4aa8b7551801f68ed40db5ee4e45
Parent:     4a13ad0bd8869bb491c67918662f9b1852595af5
Author:     Cliff Wickman <cpw@sgi.com>
AuthorDate: Thu Jan 15 09:51:20 2009 -0600
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Thu Jan 15 23:48:20 2009 +0100

    x86, UV: cpu_relax in uv_wait_completion
    
    The function uv_wait_completion() spins on reads of a memory-mapped
    register, waiting for completion of BAU hardware replies.
    
    It should call "cpu_relax()" between those reads to improve performance
    on hyperthreaded configurations.
    
    Signed-off-by: Cliff Wickman <cpw@sgi.com>
    Acked-by: Jack Steiner <steiner@sgi.org>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/tlb_uv.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/tlb_uv.c b/arch/x86/kernel/tlb_uv.c
index f885023..6812b82 100644
--- a/arch/x86/kernel/tlb_uv.c
+++ b/arch/x86/kernel/tlb_uv.c
@@ -200,6 +200,7 @@ static int uv_wait_completion(struct bau_desc *bau_desc,
 				destination_timeouts = 0;
 			}
 		}
+		cpu_relax();
 	}
 	return FLUSH_COMPLETE;
 }
--
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