path: root/include/asm-sparc64/rwsem.h
diff options
authorDavid S. Miller <davem@davemloft.net>2005-06-27 15:42:04 -0700
committerDavid S. Miller <davem@davemloft.net>2005-06-27 15:42:04 -0700
commitb445e26cbf784cdba10f2b6c3e2cd3ee7bab360a (patch)
tree8c8c377a7e5cbf608d730ec45e091e4f2b826a82 /include/asm-sparc64/rwsem.h
parent020f46a39eb7b99a575b9f4d105fce2b142acdf1 (diff)
[SPARC64]: Avoid membar instructions in delay slots.
In particular, avoid membar instructions in the delay slot of a jmpl instruction. UltraSPARC-I, II, IIi, and IIe have a bug, documented in the UltraSPARC-IIi User's Manual, Appendix K, Erratum 51 The long and short of it is that if the IMU unit misses on a branch or jmpl, and there is a store buffer synchronizing membar in the delay slot, the chip can stop fetching instructions. If interrupts are enabled or some other trap is enabled, the chip will unwedge itself, but performance will suffer. We already had a workaround for this bug in a few spots, but it's better to have the entire tree sanitized for this rule. Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/asm-sparc64/rwsem.h')
1 files changed, 2 insertions, 1 deletions
diff --git a/include/asm-sparc64/rwsem.h b/include/asm-sparc64/rwsem.h
index bf2ae90ed3d..a1cc94f9598 100644
--- a/include/asm-sparc64/rwsem.h
+++ b/include/asm-sparc64/rwsem.h
@@ -55,8 +55,9 @@ static __inline__ int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
"add %%g1, %1, %%g7\n\t"
"cas [%2], %%g1, %%g7\n\t"
"cmp %%g1, %%g7\n\t"
+ "membar #StoreLoad | #StoreStore\n\t"
"bne,pn %%icc, 1b\n\t"
- " membar #StoreLoad | #StoreStore\n\t"
+ " nop\n\t"
"mov %%g7, %0\n\t"
: "=&r" (tmp)
: "0" (tmp), "r" (sem)