From e97c5b609880d97313b13eb71830fca62cee50c2 Mon Sep 17 00:00:00 2001 From: Jim Quinlan Date: Thu, 6 Sep 2012 11:36:56 -0400 Subject: 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 Cc: linux-mips@linux-mips.org Cc: David Daney Cc: Kevin Cernekee cernekee@gmail.com Cc: Jim Quinlan Patchwork: https://patchwork.linux-mips.org/patch/4321/ Signed-off-by: Ralf Baechle --- arch/mips/lib/Makefile | 3 +- arch/mips/lib/mips-atomic.c | 176 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 178 insertions(+), 1 deletion(-) create mode 100644 arch/mips/lib/mips-atomic.c (limited to 'arch/mips/lib') diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile index a7b89371435..eeddc58802e 100644 --- a/arch/mips/lib/Makefile +++ b/arch/mips/lib/Makefile @@ -3,7 +3,8 @@ # lib-y += bitops.o csum_partial.o delay.o memcpy.o memset.o \ - strlen_user.o strncpy_user.o strnlen_user.o uncached.o + mips-atomic.o strlen_user.o strncpy_user.o \ + strnlen_user.o uncached.o obj-y += iomap.o obj-$(CONFIG_PCI) += iomap-pci.o diff --git a/arch/mips/lib/mips-atomic.c b/arch/mips/lib/mips-atomic.c new file mode 100644 index 00000000000..e091430dbeb --- /dev/null +++ b/arch/mips/lib/mips-atomic.c @@ -0,0 +1,176 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Copyright (C) 1994, 95, 96, 97, 98, 99, 2003 by Ralf Baechle + * Copyright (C) 1996 by Paul M. Antoine + * Copyright (C) 1999 Silicon Graphics + * Copyright (C) 2000 MIPS Technologies, Inc. + */ +#include +#include +#include +#include +#include + +#if !defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_MIPS_MT_SMTC) + +/* + * 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) + /* see irqflags.h for inline function */ +#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"); + +void arch_local_irq_disable(void) +{ + preempt_disable(); + __asm__ __volatile__( + "arch_local_irq_disable" + : /* no outputs */ + : /* no inputs */ + : "memory"); + preempt_enable(); +} +EXPORT_SYMBOL(arch_local_irq_disable); + + +__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) + /* see irqflags.h for inline function */ +#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"); + +unsigned long arch_local_irq_save(void) +{ + unsigned long flags; + preempt_disable(); + asm volatile("arch_local_irq_save\t%0" + : "=r" (flags) + : /* no inputs */ + : "memory"); + preempt_enable(); + return flags; +} +EXPORT_SYMBOL(arch_local_irq_save); + + +__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) + /* see irqflags.h for inline function */ +#elif defined(CONFIG_CPU_MIPSR2) + /* see irqflags.h for inline function */ +#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"); + +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 + preempt_disable(); + __asm__ __volatile__( + "arch_local_irq_restore\t%0" + : "=r" (__tmp1) + : "0" (flags) + : "memory"); + preempt_enable(); +} +EXPORT_SYMBOL(arch_local_irq_restore); + + +void __arch_local_irq_restore(unsigned long flags) +{ + unsigned long __tmp1; + + preempt_disable(); + __asm__ __volatile__( + "arch_local_irq_restore\t%0" + : "=r" (__tmp1) + : "0" (flags) + : "memory"); + preempt_enable(); +} +EXPORT_SYMBOL(__arch_local_irq_restore); + +#endif /* !defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_MIPS_MT_SMTC) */ -- cgit v1.2.3