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authorDavid S. Miller <davem@davemloft.net>2005-09-08 17:37:53 -0400
committerDavid S. Miller <davem@davemloft.net>2005-09-08 17:37:53 -0400
commit4d803fcdcd97dd346d4b39c3b76e5879cead8a31 (patch)
treef30c8caa998261fc0983121021184f0f6cc555b4 /include
parent1b11d78cf87a7014f96e5b7fa2e1233cc8081a00 (diff)
[SPARC64]: Inline membar()'s again.
Since GCC has to emit a call and a delay slot to the out-of-line "membar" routines in arch/sparc64/lib/mb.S it is much better to just do the necessary predicted branch inline instead as: ba,pt %xcc, 1f membar #whatever 1: instead of the current: call membar_foo dslot because this way GCC is not required to allocate a stack frame if the function can be a leaf function. This also makes this bug fix easier to backport to 2.4.x Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/asm-sparc64/system.h49
1 files changed, 42 insertions, 7 deletions
diff --git a/include/asm-sparc64/system.h b/include/asm-sparc64/system.h
index 5e94c05dc2fc..b5417529f6f1 100644
--- a/include/asm-sparc64/system.h
+++ b/include/asm-sparc64/system.h
@@ -28,13 +28,48 @@ enum sparc_cpu {
28#define ARCH_SUN4C_SUN4 0 28#define ARCH_SUN4C_SUN4 0
29#define ARCH_SUN4 0 29#define ARCH_SUN4 0
30 30
31extern void mb(void); 31/* These are here in an effort to more fully work around Spitfire Errata
32extern void rmb(void); 32 * #51. Essentially, if a memory barrier occurs soon after a mispredicted
33extern void wmb(void); 33 * branch, the chip can stop executing instructions until a trap occurs.
34extern void membar_storeload(void); 34 * Therefore, if interrupts are disabled, the chip can hang forever.
35extern void membar_storeload_storestore(void); 35 *
36extern void membar_storeload_loadload(void); 36 * It used to be believed that the memory barrier had to be right in the
37extern void membar_storestore_loadstore(void); 37 * delay slot, but a case has been traced recently wherein the memory barrier
38 * was one instruction after the branch delay slot and the chip still hung.
39 * The offending sequence was the following in sym_wakeup_done() of the
40 * sym53c8xx_2 driver:
41 *
42 * call sym_ccb_from_dsa, 0
43 * movge %icc, 0, %l0
44 * brz,pn %o0, .LL1303
45 * mov %o0, %l2
46 * membar #LoadLoad
47 *
48 * The branch has to be mispredicted for the bug to occur. Therefore, we put
49 * the memory barrier explicitly into a "branch always, predicted taken"
50 * delay slot to avoid the problem case.
51 */
52#define membar_safe(type) \
53do { __asm__ __volatile__("ba,pt %%xcc, 1f\n\t" \
54 " membar " type "\n" \
55 "1:\n" \
56 : : : "memory"); \
57} while (0)
58
59#define mb() \
60 membar_safe("#LoadLoad | #LoadStore | #StoreStore | #StoreLoad")
61#define rmb() \
62 membar_safe("#LoadLoad")
63#define wmb() \
64 membar_safe("#StoreStore")
65#define membar_storeload() \
66 membar_safe("#StoreLoad")
67#define membar_storeload_storestore() \
68 membar_safe("#StoreLoad | #StoreStore")
69#define membar_storeload_loadload() \
70 membar_safe("#StoreLoad | #LoadLoad")
71#define membar_storestore_loadstore() \
72 membar_safe("#StoreStore | #LoadStore")
38 73
39#endif 74#endif
40 75