[PATCH] Directed yield: direct yield of spinlocks for s390.

Use the new diagnose 0x9c in the spinlock implementation for s390.  It
yields the remaining timeslice of the virtual cpu that tries to acquire a
lock to the virtual cpu that is the current holder of the lock.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 48998d50b00a..b30e5897cdf7 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -251,6 +251,17 @@ startup_continue:
 0:
 
 #
+# find out if the diag 0x9c is available
+#
+        la     %r1,0f-.LPG1(%r13)       # set program check address
+        stg    %r1,__LC_PGM_NEW_PSW+8
+        stap   __LC_CPUID+4             # store cpu address
+        lh     %r1,__LC_CPUID+4
+        diag   %r1,0,0x9c               # test diag 0x9c
+        oi     6(%r12),1                # set diag9c flag
+0:
+
+#
 # find out if we have the MVCOS instruction
 #
         la      %r1,0f-.LPG1(%r13)      # set program check address