Hi Maciej,
On 05/12/16 16:20, Maciej W. Rozycki wrote:
On Fri, 2 Dec 2016, Matt Redfearn wrote:
diff --git a/arch/mips/include/asm/stackframe.h b/arch/mips/include/asm/stackframe.h
index eebf39549606..5782fa3d63be 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -216,12 +216,22 @@
LONG_S $25, PT_R25(sp)
LONG_S $28, PT_R28(sp)
LONG_S $31, PT_R31(sp)
+
+ /* Set thread_info if we're coming from user mode */
+ .set reorder
+ mfc0 k0, CP0_STATUS
+ sll k0, 3 /* extract cu0 bit */
+ .set noreorder
+ bltz k0, 9f
+ nop
This code is already `.set reorder', although a badly applied CONFIG_EVA
change made things slightly less obvious. So why do you need this `.set
reorder' in the first place, and then why do you switch code that follows
to `.set noreorder'?
Ah yes, I missed the .set reorder above the EVA ifdef and just included
the .set reorder as the similar snippet here:
http://lxr.free-electrons.com/source/arch/mips/include/asm/stackframe.h#L149
I'll revise that in V2.
Thanks,
Matt
Overall I think all <asm/stackframe.h> code should be using the (default)
`.set reorder' mode, perhaps forced explicitly in case these macros are
pasted into `.set noreorder' code, to make it easier to avoid subtle data
dependency bugs, and also to make R6 porting easier. Except maybe for the
RFE sequence, for readability's sake, although even there GAS will do the
right thing. Surely the BLTZ/MOVE piece does not have to be `.set
noreorder' as GAS will schedule that delay slot automatically if allowed
to.
Maciej
