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sparc64: Make lock backoff really a NOP on UP builds.

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As noticed by Mikulas Patocka, the backoff macros don't
completely nop out for UP builds, we still get a
branch always and a delay slot nop.

Fix this by making the branch to the backoff spin loop
selective, then we can nop out the spin loop completely.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller
2010-08-18 22:53:26 -07:00
parent 6ec274750c
commit 0f58189d4a
3 changed files with 22 additions and 17 deletions
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11
arch/sparc/include/asm/backoff.h
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@@ -8,6 +8,9 @@
#define BACKOFF_SETUP(reg) \
mov 1, reg
#define BACKOFF_LABEL(spin_label, continue_label) \
spin_label
#define BACKOFF_SPIN(reg, tmp, label) \
mov reg, tmp; \
88: brnz,pt tmp, 88b; \
@@ -22,9 +25,11 @@
#else
#define BACKOFF_SETUP(reg)
#define BACKOFF_SPIN(reg, tmp, label) \
ba,pt %xcc, label; \
nop;
#define BACKOFF_LABEL(spin_label, continue_label) \
continue_label
#define BACKOFF_SPIN(reg, tmp, label)
#endif