2.6.25-stable review patch. If anyone has any objections, please let us know.

------------------

From: Andrea Shepard

[ Upstream commit e0037df3852b4b60edbe01f70f4968e4a9fdb272 ]

Make arch/sparc64/kernel/trampoline.S in 2.6.27.1 lock prom_entry_lock
when calling the PROM. This prevents a race condition that I observed
causing a hang on startup on a 12-CPU E4500.

I am not subscribed to this list, so please CC me on replies.

Signed-off-by: Andrea Shepard
Signed-off-by: David S. Miller
Signed-off-by: Greg Kroah-Hartman

---
arch/sparc64/kernel/trampoline.S | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)

--- a/arch/sparc64/kernel/trampoline.S
+++ b/arch/sparc64/kernel/trampoline.S
@@ -328,6 +328,12 @@ after_lock_tlb:

wrpr %g0, 0, %wstate

+ sethi %hi(prom_entry_lock), %g2
+1: ldstub [%g2 + %lo(prom_entry_lock)], %g1
+ membar #StoreLoad | #StoreStore
+ brnz,pn %g1, 1b
+ nop
+
/* As a hack, put &init_thread_union into %g6.
* prom_world() loads from here to restore the %asi
* register.
@@ -337,7 +343,7 @@ after_lock_tlb:

sethi %hi(is_sun4v), %o0
lduw [%o0 + %lo(is_sun4v)], %o0
- brz,pt %o0, 1f
+ brz,pt %o0, 2f
nop

TRAP_LOAD_TRAP_BLOCK(%g2, %g3)
@@ -369,10 +375,10 @@ after_lock_tlb:
call %o1
add %sp, (2047 + 128), %o0

- ba,pt %xcc, 2f
+ ba,pt %xcc, 3f
nop

-1: sethi %hi(sparc64_ttable_tl0), %o0
+2: sethi %hi(sparc64_ttable_tl0), %o0
set prom_set_trap_table_name, %g2
stx %g2, [%sp + 2047 + 128 + 0x00]
mov 1, %g2
@@ -386,7 +392,11 @@ after_lock_tlb:
call %o1
add %sp, (2047 + 128), %o0

-2: ldx [%l0], %g6
+3: sethi %hi(prom_entry_lock), %g2
+ stb %g0, [%g2 + %lo(prom_entry_lock)]
+ membar #StoreStore | #StoreLoad
+
+ ldx [%l0], %g6
ldx [%g6 + TI_TASK], %g4

mov 1, %g5

--
--
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