MIPS: Make local_irq_disable macro safe for non-Mipsr2
For non-mipsr2 processors, the local_irq_disable contains an mfc0-mtc0
pair with instructions inbetween. With preemption enabled, this sequence
may get preempted and effect a stale value of CP0_STATUS when executing
the mtc0 instruction. This commit avoids this scenario by incrementing
the preempt count before the mfc0 and decrementing it after the mtc9.
[ralf@linux-mips.org: This patch is sorting out the part that were missed
by e97c5b6098 [MIPS: Make irqflags.h functions preempt-safe for non-mipsr2
cpus.] I also re-enabled the inclusion of <asm/asm-offsets.h> at the top
of <asm/asmmacro.h>].
Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: cernekee@gmail.com
Patchwork: https://patchwork.linux-mips.org/patch/6164/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/include/asm/asmmacro.h b/arch/mips/include/asm/asmmacro.h
index 69a9a22..4225e99 100644
--- a/arch/mips/include/asm/asmmacro.h
+++ b/arch/mips/include/asm/asmmacro.h
@@ -9,6 +9,7 @@
#define _ASM_ASMMACRO_H
#include <asm/hazards.h>
+#include <asm/asm-offsets.h>
#ifdef CONFIG_32BIT
#include <asm/asmmacro-32.h>
@@ -54,11 +55,21 @@
.endm
.macro local_irq_disable reg=t0
+#ifdef CONFIG_PREEMPT
+ lw \reg, TI_PRE_COUNT($28)
+ addi \reg, \reg, 1
+ sw \reg, TI_PRE_COUNT($28)
+#endif
mfc0 \reg, CP0_STATUS
ori \reg, \reg, 1
xori \reg, \reg, 1
mtc0 \reg, CP0_STATUS
irq_disable_hazard
+#ifdef CONFIG_PREEMPT
+ lw \reg, TI_PRE_COUNT($28)
+ addi \reg, \reg, -1
+ sw \reg, TI_PRE_COUNT($28)
+#endif
.endm
#endif /* CONFIG_MIPS_MT_SMTC */