MIPS: Make local_irq_disable macro safe for non-Mipsr2
authorJim Quinlan <jim2101024@gmail.com>
Wed, 27 Nov 2013 20:34:50 +0000 (15:34 -0500)
committerRalf Baechle <ralf@linux-mips.org>
Thu, 20 Mar 2014 12:46:15 +0000 (13:46 +0100)
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>
arch/mips/include/asm/asmmacro.h

index 69a9a22..4225e99 100644 (file)
@@ -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>
        .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 */