linux_dsm_epyc7002/arch/mips/include/asm/irqflags.h
Jim Quinlan e97c5b6098 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>
2012-11-09 10:59:21 +01:00

232 lines
5.1 KiB
C

/*
* 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.
*/
#ifndef _ASM_IRQFLAGS_H
#define _ASM_IRQFLAGS_H
#ifndef __ASSEMBLY__
#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"
" .set reorder \n"
" .set noat \n"
#ifdef CONFIG_MIPS_MT_SMTC
" mfc0 $1, $2, 1 # SMTC - clear TCStatus.IXMT \n"
" ori $1, 0x400 \n"
" xori $1, 0x400 \n"
" mtc0 $1, $2, 1 \n"
#elif defined(CONFIG_CPU_MIPSR2)
" ei \n"
#else
" mfc0 $1,$12 \n"
" ori $1,0x1f \n"
" xori $1,0x1e \n"
" mtc0 $1,$12 \n"
#endif
" irq_enable_hazard \n"
" .set pop \n"
" .endm");
extern void smtc_ipi_replay(void);
static inline void arch_local_irq_enable(void)
{
#ifdef CONFIG_MIPS_MT_SMTC
/*
* SMTC kernel needs to do a software replay of queued
* IPIs, at the cost of call overhead on each local_irq_enable()
*/
smtc_ipi_replay();
#endif
__asm__ __volatile__(
"arch_local_irq_enable"
: /* no outputs */
: /* no inputs */
: "memory");
}
__asm__(
" .macro arch_local_save_flags flags \n"
" .set push \n"
" .set reorder \n"
#ifdef CONFIG_MIPS_MT_SMTC
" mfc0 \\flags, $2, 1 \n"
#else
" mfc0 \\flags, $12 \n"
#endif
" .set pop \n"
" .endm \n");
static inline unsigned long arch_local_save_flags(void)
{
unsigned long flags;
asm volatile("arch_local_save_flags %0" : "=r" (flags));
return flags;
}
static inline int arch_irqs_disabled_flags(unsigned long flags)
{
#ifdef CONFIG_MIPS_MT_SMTC
/*
* SMTC model uses TCStatus.IXMT to disable interrupts for a thread/CPU
*/
return flags & 0x400;
#else
return !(flags & 1);
#endif
}
#endif /* #ifndef __ASSEMBLY__ */
/*
* Do the CPU's IRQ-state tracing from assembly code.
*/
#ifdef CONFIG_TRACE_IRQFLAGS
/* Reload some registers clobbered by trace_hardirqs_on */
#ifdef CONFIG_64BIT
# define TRACE_IRQS_RELOAD_REGS \
LONG_L $11, PT_R11(sp); \
LONG_L $10, PT_R10(sp); \
LONG_L $9, PT_R9(sp); \
LONG_L $8, PT_R8(sp); \
LONG_L $7, PT_R7(sp); \
LONG_L $6, PT_R6(sp); \
LONG_L $5, PT_R5(sp); \
LONG_L $4, PT_R4(sp); \
LONG_L $2, PT_R2(sp)
#else
# define TRACE_IRQS_RELOAD_REGS \
LONG_L $7, PT_R7(sp); \
LONG_L $6, PT_R6(sp); \
LONG_L $5, PT_R5(sp); \
LONG_L $4, PT_R4(sp); \
LONG_L $2, PT_R2(sp)
#endif
# define TRACE_IRQS_ON \
CLI; /* make sure trace_hardirqs_on() is called in kernel level */ \
jal trace_hardirqs_on
# define TRACE_IRQS_ON_RELOAD \
TRACE_IRQS_ON; \
TRACE_IRQS_RELOAD_REGS
# define TRACE_IRQS_OFF \
jal trace_hardirqs_off
#else
# define TRACE_IRQS_ON
# define TRACE_IRQS_ON_RELOAD
# define TRACE_IRQS_OFF
#endif
#endif /* _ASM_IRQFLAGS_H */