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e97c5b6098
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>
177 lines
4.3 KiB
C
177 lines
4.3 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 1994, 95, 96, 97, 98, 99, 2003 by Ralf Baechle
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* Copyright (C) 1996 by Paul M. Antoine
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* Copyright (C) 1999 Silicon Graphics
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* Copyright (C) 2000 MIPS Technologies, Inc.
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*/
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#include <asm/irqflags.h>
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#include <asm/hazards.h>
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#include <linux/compiler.h>
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#include <linux/preempt.h>
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#include <linux/export.h>
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#if !defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_MIPS_MT_SMTC)
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/*
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* For cli() we have to insert nops to make sure that the new value
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* has actually arrived in the status register before the end of this
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* macro.
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* R4000/R4400 need three nops, the R4600 two nops and the R10000 needs
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* no nops at all.
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*/
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/*
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* For TX49, operating only IE bit is not enough.
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*
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* If mfc0 $12 follows store and the mfc0 is last instruction of a
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* page and fetching the next instruction causes TLB miss, the result
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* of the mfc0 might wrongly contain EXL bit.
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*
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* ERT-TX49H2-027, ERT-TX49H3-012, ERT-TX49HL3-006, ERT-TX49H4-008
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*
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* Workaround: mask EXL bit of the result or place a nop before mfc0.
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*/
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__asm__(
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" .macro arch_local_irq_disable\n"
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" .set push \n"
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" .set noat \n"
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#ifdef CONFIG_MIPS_MT_SMTC
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" mfc0 $1, $2, 1 \n"
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" ori $1, 0x400 \n"
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" .set noreorder \n"
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" mtc0 $1, $2, 1 \n"
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#elif defined(CONFIG_CPU_MIPSR2)
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/* see irqflags.h for inline function */
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#else
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" mfc0 $1,$12 \n"
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" ori $1,0x1f \n"
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" xori $1,0x1f \n"
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" .set noreorder \n"
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" mtc0 $1,$12 \n"
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#endif
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" irq_disable_hazard \n"
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" .set pop \n"
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" .endm \n");
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void arch_local_irq_disable(void)
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{
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preempt_disable();
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__asm__ __volatile__(
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"arch_local_irq_disable"
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: /* no outputs */
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: /* no inputs */
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: "memory");
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preempt_enable();
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}
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EXPORT_SYMBOL(arch_local_irq_disable);
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__asm__(
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" .macro arch_local_irq_save result \n"
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" .set push \n"
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" .set reorder \n"
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" .set noat \n"
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#ifdef CONFIG_MIPS_MT_SMTC
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" mfc0 \\result, $2, 1 \n"
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" ori $1, \\result, 0x400 \n"
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" .set noreorder \n"
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" mtc0 $1, $2, 1 \n"
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" andi \\result, \\result, 0x400 \n"
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#elif defined(CONFIG_CPU_MIPSR2)
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/* see irqflags.h for inline function */
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#else
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" mfc0 \\result, $12 \n"
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" ori $1, \\result, 0x1f \n"
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" xori $1, 0x1f \n"
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" .set noreorder \n"
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" mtc0 $1, $12 \n"
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#endif
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" irq_disable_hazard \n"
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" .set pop \n"
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" .endm \n");
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unsigned long arch_local_irq_save(void)
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{
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unsigned long flags;
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preempt_disable();
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asm volatile("arch_local_irq_save\t%0"
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: "=r" (flags)
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: /* no inputs */
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: "memory");
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preempt_enable();
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return flags;
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}
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EXPORT_SYMBOL(arch_local_irq_save);
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__asm__(
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" .macro arch_local_irq_restore flags \n"
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" .set push \n"
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" .set noreorder \n"
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" .set noat \n"
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#ifdef CONFIG_MIPS_MT_SMTC
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"mfc0 $1, $2, 1 \n"
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"andi \\flags, 0x400 \n"
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"ori $1, 0x400 \n"
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"xori $1, 0x400 \n"
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"or \\flags, $1 \n"
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"mtc0 \\flags, $2, 1 \n"
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#elif defined(CONFIG_CPU_MIPSR2) && defined(CONFIG_IRQ_CPU)
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/* see irqflags.h for inline function */
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#elif defined(CONFIG_CPU_MIPSR2)
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/* see irqflags.h for inline function */
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#else
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" mfc0 $1, $12 \n"
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" andi \\flags, 1 \n"
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" ori $1, 0x1f \n"
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" xori $1, 0x1f \n"
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" or \\flags, $1 \n"
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" mtc0 \\flags, $12 \n"
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#endif
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" irq_disable_hazard \n"
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" .set pop \n"
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" .endm \n");
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void arch_local_irq_restore(unsigned long flags)
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{
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unsigned long __tmp1;
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#ifdef CONFIG_MIPS_MT_SMTC
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/*
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* SMTC kernel needs to do a software replay of queued
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* IPIs, at the cost of branch and call overhead on each
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* local_irq_restore()
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*/
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if (unlikely(!(flags & 0x0400)))
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smtc_ipi_replay();
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#endif
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preempt_disable();
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__asm__ __volatile__(
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"arch_local_irq_restore\t%0"
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: "=r" (__tmp1)
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: "0" (flags)
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: "memory");
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preempt_enable();
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}
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EXPORT_SYMBOL(arch_local_irq_restore);
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void __arch_local_irq_restore(unsigned long flags)
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{
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unsigned long __tmp1;
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preempt_disable();
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__asm__ __volatile__(
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"arch_local_irq_restore\t%0"
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: "=r" (__tmp1)
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: "0" (flags)
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: "memory");
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preempt_enable();
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}
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EXPORT_SYMBOL(__arch_local_irq_restore);
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#endif /* !defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_MIPS_MT_SMTC) */
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