MIPS: Make irqflags.h functions preempt-safe for non-mipsr2 cpus
For non MIPSr2 processors, such as the BMIPS 5000, calls to
arch_local_irq_disable() and others may be preempted, and in doing
so a stale value may be restored to c0_status. This fix disables
preemption for such processors prior to the call and enables it
after the call.
Those functions that needed this fix have been "outlined" to
mips-atomic.c, as they are no longer good candidates for inlining.
This bug was observed in a BMIPS 5000, occuring once every few hours
in a continuous reboot test. It was traced to the write_lock_irq()
function which was being invoked in release_task() in exit.c.
By placing a number of "nops" inbetween the mfc0/mtc0 pair in
arch_local_irq_disable(), which is called by write_lock_irq(), we
were able to greatly increase the occurance of this bug. Similarly,
the application of this commit silenced the bug.
Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: David Daney <ddaney.cavm@gmail.com>
Cc: Kevin Cernekee cernekee@gmail.com
Cc: Jim Quinlan <jim2101024@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/4321/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/include/asm/irqflags.h b/arch/mips/include/asm/irqflags.h
index 309cbcd..9f3384c 100644
--- a/arch/mips/include/asm/irqflags.h
+++ b/arch/mips/include/asm/irqflags.h
@@ -16,6 +16,105 @@
#include <linux/compiler.h>
#include <asm/hazards.h>
+#if defined(CONFIG_CPU_MIPSR2) && !defined(CONFIG_MIPS_MT_SMTC)
+
+__asm__(
+ " .macro arch_local_irq_disable\n"
+ " .set push \n"
+ " .set noat \n"
+ " di \n"
+ " irq_disable_hazard \n"
+ " .set pop \n"
+ " .endm \n");
+
+static inline void arch_local_irq_disable(void)
+{
+ __asm__ __volatile__(
+ "arch_local_irq_disable"
+ : /* no outputs */
+ : /* no inputs */
+ : "memory");
+}
+
+
+__asm__(
+ " .macro arch_local_irq_save result \n"
+ " .set push \n"
+ " .set reorder \n"
+ " .set noat \n"
+ " di \\result \n"
+ " andi \\result, 1 \n"
+ " irq_disable_hazard \n"
+ " .set pop \n"
+ " .endm \n");
+
+static inline unsigned long arch_local_irq_save(void)
+{
+ unsigned long flags;
+ asm volatile("arch_local_irq_save\t%0"
+ : "=r" (flags)
+ : /* no inputs */
+ : "memory");
+ return flags;
+}
+
+
+__asm__(
+ " .macro arch_local_irq_restore flags \n"
+ " .set push \n"
+ " .set noreorder \n"
+ " .set noat \n"
+#if defined(CONFIG_IRQ_CPU)
+ /*
+ * Slow, but doesn't suffer from a relatively unlikely race
+ * condition we're having since days 1.
+ */
+ " beqz \\flags, 1f \n"
+ " di \n"
+ " ei \n"
+ "1: \n"
+#else
+ /*
+ * Fast, dangerous. Life is fun, life is good.
+ */
+ " mfc0 $1, $12 \n"
+ " ins $1, \\flags, 0, 1 \n"
+ " mtc0 $1, $12 \n"
+#endif
+ " irq_disable_hazard \n"
+ " .set pop \n"
+ " .endm \n");
+
+static inline void arch_local_irq_restore(unsigned long flags)
+{
+ unsigned long __tmp1;
+
+ __asm__ __volatile__(
+ "arch_local_irq_restore\t%0"
+ : "=r" (__tmp1)
+ : "0" (flags)
+ : "memory");
+}
+
+static inline void __arch_local_irq_restore(unsigned long flags)
+{
+ unsigned long __tmp1;
+
+ __asm__ __volatile__(
+ "arch_local_irq_restore\t%0"
+ : "=r" (__tmp1)
+ : "0" (flags)
+ : "memory");
+}
+#else
+/* Functions that require preempt_{dis,en}able() are in mips-atomic.c */
+void arch_local_irq_disable(void);
+unsigned long arch_local_irq_save(void);
+void arch_local_irq_restore(unsigned long flags);
+void __arch_local_irq_restore(unsigned long flags);
+#endif /* if defined(CONFIG_CPU_MIPSR2) && !defined(CONFIG_MIPS_MT_SMTC) */
+
+
__asm__(
" .macro arch_local_irq_enable \n"
" .set push \n"
@@ -57,55 +156,6 @@
}
-/*
- * For cli() we have to insert nops to make sure that the new value
- * has actually arrived in the status register before the end of this
- * macro.
- * R4000/R4400 need three nops, the R4600 two nops and the R10000 needs
- * no nops at all.
- */
-/*
- * For TX49, operating only IE bit is not enough.
- *
- * If mfc0 $12 follows store and the mfc0 is last instruction of a
- * page and fetching the next instruction causes TLB miss, the result
- * of the mfc0 might wrongly contain EXL bit.
- *
- * ERT-TX49H2-027, ERT-TX49H3-012, ERT-TX49HL3-006, ERT-TX49H4-008
- *
- * Workaround: mask EXL bit of the result or place a nop before mfc0.
- */
-__asm__(
- " .macro arch_local_irq_disable\n"
- " .set push \n"
- " .set noat \n"
-#ifdef CONFIG_MIPS_MT_SMTC
- " mfc0 $1, $2, 1 \n"
- " ori $1, 0x400 \n"
- " .set noreorder \n"
- " mtc0 $1, $2, 1 \n"
-#elif defined(CONFIG_CPU_MIPSR2)
- " di \n"
-#else
- " mfc0 $1,$12 \n"
- " ori $1,0x1f \n"
- " xori $1,0x1f \n"
- " .set noreorder \n"
- " mtc0 $1,$12 \n"
-#endif
- " irq_disable_hazard \n"
- " .set pop \n"
- " .endm \n");
-
-static inline void arch_local_irq_disable(void)
-{
- __asm__ __volatile__(
- "arch_local_irq_disable"
- : /* no outputs */
- : /* no inputs */
- : "memory");
-}
-
__asm__(
" .macro arch_local_save_flags flags \n"
" .set push \n"
@@ -125,113 +175,6 @@
return flags;
}
-__asm__(
- " .macro arch_local_irq_save result \n"
- " .set push \n"
- " .set reorder \n"
- " .set noat \n"
-#ifdef CONFIG_MIPS_MT_SMTC
- " mfc0 \\result, $2, 1 \n"
- " ori $1, \\result, 0x400 \n"
- " .set noreorder \n"
- " mtc0 $1, $2, 1 \n"
- " andi \\result, \\result, 0x400 \n"
-#elif defined(CONFIG_CPU_MIPSR2)
- " di \\result \n"
- " andi \\result, 1 \n"
-#else
- " mfc0 \\result, $12 \n"
- " ori $1, \\result, 0x1f \n"
- " xori $1, 0x1f \n"
- " .set noreorder \n"
- " mtc0 $1, $12 \n"
-#endif
- " irq_disable_hazard \n"
- " .set pop \n"
- " .endm \n");
-
-static inline unsigned long arch_local_irq_save(void)
-{
- unsigned long flags;
- asm volatile("arch_local_irq_save\t%0"
- : "=r" (flags)
- : /* no inputs */
- : "memory");
- return flags;
-}
-
-__asm__(
- " .macro arch_local_irq_restore flags \n"
- " .set push \n"
- " .set noreorder \n"
- " .set noat \n"
-#ifdef CONFIG_MIPS_MT_SMTC
- "mfc0 $1, $2, 1 \n"
- "andi \\flags, 0x400 \n"
- "ori $1, 0x400 \n"
- "xori $1, 0x400 \n"
- "or \\flags, $1 \n"
- "mtc0 \\flags, $2, 1 \n"
-#elif defined(CONFIG_CPU_MIPSR2) && defined(CONFIG_IRQ_CPU)
- /*
- * Slow, but doesn't suffer from a relatively unlikely race
- * condition we're having since days 1.
- */
- " beqz \\flags, 1f \n"
- " di \n"
- " ei \n"
- "1: \n"
-#elif defined(CONFIG_CPU_MIPSR2)
- /*
- * Fast, dangerous. Life is fun, life is good.
- */
- " mfc0 $1, $12 \n"
- " ins $1, \\flags, 0, 1 \n"
- " mtc0 $1, $12 \n"
-#else
- " mfc0 $1, $12 \n"
- " andi \\flags, 1 \n"
- " ori $1, 0x1f \n"
- " xori $1, 0x1f \n"
- " or \\flags, $1 \n"
- " mtc0 \\flags, $12 \n"
-#endif
- " irq_disable_hazard \n"
- " .set pop \n"
- " .endm \n");
-
-
-static inline void arch_local_irq_restore(unsigned long flags)
-{
- unsigned long __tmp1;
-
-#ifdef CONFIG_MIPS_MT_SMTC
- /*
- * SMTC kernel needs to do a software replay of queued
- * IPIs, at the cost of branch and call overhead on each
- * local_irq_restore()
- */
- if (unlikely(!(flags & 0x0400)))
- smtc_ipi_replay();
-#endif
-
- __asm__ __volatile__(
- "arch_local_irq_restore\t%0"
- : "=r" (__tmp1)
- : "0" (flags)
- : "memory");
-}
-
-static inline void __arch_local_irq_restore(unsigned long flags)
-{
- unsigned long __tmp1;
-
- __asm__ __volatile__(
- "arch_local_irq_restore\t%0"
- : "=r" (__tmp1)
- : "0" (flags)
- : "memory");
-}
static inline int arch_irqs_disabled_flags(unsigned long flags)
{
@@ -245,7 +188,7 @@
#endif
}
-#endif
+#endif /* #ifndef __ASSEMBLY__ */
/*
* Do the CPU's IRQ-state tracing from assembly code.