linux/arch/sparc/include/asm/backoff.h
David S. Miller 0f58189d4a sparc64: Make lock backoff really a NOP on UP builds.
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>
2010-08-18 22:53:26 -07:00

37 lines
618 B
C

#ifndef _SPARC64_BACKOFF_H
#define _SPARC64_BACKOFF_H
#define BACKOFF_LIMIT (4 * 1024)
#ifdef CONFIG_SMP
#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; \
sub tmp, 1, tmp; \
set BACKOFF_LIMIT, tmp; \
cmp reg, tmp; \
bg,pn %xcc, label; \
nop; \
ba,pt %xcc, label; \
sllx reg, 1, reg;
#else
#define BACKOFF_SETUP(reg)
#define BACKOFF_LABEL(spin_label, continue_label) \
continue_label
#define BACKOFF_SPIN(reg, tmp, label)
#endif
#endif /* _SPARC64_BACKOFF_H */