PERFORCE change 206500 for review

[Robert Watson]

http://p4web.freebsd.org/@@206500?ac=10

Change 206500 by rwatson at rwatson_svr_ctsrd_mipsbuild on 2012/02/18 14:15:58

	Condition more use of the MIPS4k 'sync' instruction on options
	SMP in the FreeBSD kernel.  Normally the instruction would degrade
	to a 'nop' on UP MIPS hardware, but not currently our MIPS hardware.
	However, it may be worth making this change in FreeBSD as well,
	since we believe these instructions aren't required -- something to
	confirm with hard-core MIPS hackers.

Affected files ...

.. //depot/projects/ctsrd/beribsd/src/sys/mips/include/atomic.h#2 edit
.. //depot/projects/ctsrd/beribsd/src/sys/mips/mips/exception.S#2 edit
.. //depot/projects/ctsrd/beribsd/src/sys/mips/mips/swtch.S#2 edit

Differences ...

==== //depot/projects/ctsrd/beribsd/src/sys/mips/include/atomic.h#2 (text+ko) ====

@@ -49,7 +49,9 @@
 mips_sync(void)
 {
 	__asm __volatile (".set noreorder\n\t"
+#ifdef SMP
 			"sync\n\t"
+#endif
 			"nop\n\t"
 			"nop\n\t"
 			"nop\n\t"

==== //depot/projects/ctsrd/beribsd/src/sys/mips/mips/exception.S#2 (text+ko) ====

@@ -387,7 +387,9 @@
 	or	a1, a1, a0
 	SAVE_REG(a1, SR, sp)
 	RESTORE_CPU			# v0 contains the return address.
+#ifdef SMP
 	sync
+#endif
 	eret
 	.set	at
 END(MipsKernGenException)
@@ -553,7 +555,9 @@
 
 	mtc0	k0, MIPS_COP_0_STATUS	# still exception level
 	ITLBNOPFIX
+#ifdef SMP
 	sync
+#endif
 	eret
 	.set	at
 END(MipsUserGenException)
@@ -645,7 +649,9 @@
 	SAVE_REG(a1, SR, sp)
 	REG_L	v0, CALLFRAME_RA + KERN_REG_SIZE(sp)
 	RESTORE_CPU			# v0 contains the return address.
+#ifdef SMP
 	sync
+#endif
 	eret
 	.set	at
 END(MipsKernIntr)
@@ -820,7 +826,9 @@
 
 	mtc0	k0, MIPS_COP_0_STATUS	# SR with EXL set. 
 	ITLBNOPFIX
+#ifdef SMP
 	sync
+#endif
 	eret
 	.set	at
 END(MipsUserIntr)

==== //depot/projects/ctsrd/beribsd/src/sys/mips/mips/swtch.S#2 (text+ko) ====

@@ -160,7 +160,9 @@
 	or	k0, k0, k1
 	mtc0	k0, MIPS_COP_0_STATUS	# switch to user mode (when eret...)
 	HAZARD_DELAY
+#ifdef SMP
 	sync
+#endif
 	eret
 	.set	at
 END(fork_trampoline)