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. [[email protected]: This patch is sorting out the part that were missed by e97c5b6 [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 <[email protected]> Cc: [email protected] Cc: [email protected] Patchwork: https://patchwork.linux-mips.org/patch/6164/ Signed-off-by: Ralf Baechle <[email protected]>
ddstreet · Mar 20, 2014 · 71ca758 · 71ca758
1 parent 2eddb70
commit 71ca758
Showing 1 changed file with 11 additions and 0 deletions.
diff --git 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 */