linux/arch/mips/lib/mips-atomic.c
Tiezhu Yang 78cf0eb926 MIPS: Fix kernel hang under FUNCTION_GRAPH_TRACER and PREEMPT_TRACER
When update the latest mainline kernel with the following three configs,
the kernel hangs during startup:

(1) CONFIG_FUNCTION_GRAPH_TRACER=y
(2) CONFIG_PREEMPT_TRACER=y
(3) CONFIG_FTRACE_STARTUP_TEST=y

When update the latest mainline kernel with the above two configs (1)
and (2), the kernel starts normally, but it still hangs when execute
the following command:

echo "function_graph" > /sys/kernel/debug/tracing/current_tracer

Without CONFIG_PREEMPT_TRACER=y, the above two kinds of kernel hangs
disappeared, so it seems that CONFIG_PREEMPT_TRACER has some influences
with function_graph tracer at the first glance.

I use ejtag to find out the epc address is related with preempt_enable()
in the file arch/mips/lib/mips-atomic.c, because function tracing can
trace the preempt_{enable,disable} calls that are traced, replace them
with preempt_{enable,disable}_notrace to prevent function tracing from
going into an infinite loop, and then it can fix the kernel hang issue.

By the way, it seems that this commit is a complement and improvement of
commit f93a1a00f2 ("MIPS: Fix crash that occurs when function tracing
is enabled").

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
2021-05-25 15:33:17 +02:00

114 lines
2.7 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.
*/
#include <asm/irqflags.h>
#include <asm/hazards.h>
#include <linux/compiler.h>
#include <linux/preempt.h>
#include <linux/export.h>
#include <linux/stringify.h>
#if !defined(CONFIG_CPU_HAS_DIEI)
/*
* 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.
*/
notrace void arch_local_irq_disable(void)
{
preempt_disable_notrace();
__asm__ __volatile__(
" .set push \n"
" .set noat \n"
" mfc0 $1,$12 \n"
" ori $1,0x1f \n"
" xori $1,0x1f \n"
" .set noreorder \n"
" mtc0 $1,$12 \n"
" " __stringify(__irq_disable_hazard) " \n"
" .set pop \n"
: /* no outputs */
: /* no inputs */
: "memory");
preempt_enable_notrace();
}
EXPORT_SYMBOL(arch_local_irq_disable);
notrace unsigned long arch_local_irq_save(void)
{
unsigned long flags;
preempt_disable_notrace();
__asm__ __volatile__(
" .set push \n"
" .set reorder \n"
" .set noat \n"
" mfc0 %[flags], $12 \n"
" ori $1, %[flags], 0x1f \n"
" xori $1, 0x1f \n"
" .set noreorder \n"
" mtc0 $1, $12 \n"
" " __stringify(__irq_disable_hazard) " \n"
" .set pop \n"
: [flags] "=r" (flags)
: /* no inputs */
: "memory");
preempt_enable_notrace();
return flags;
}
EXPORT_SYMBOL(arch_local_irq_save);
notrace void arch_local_irq_restore(unsigned long flags)
{
unsigned long __tmp1;
preempt_disable_notrace();
__asm__ __volatile__(
" .set push \n"
" .set noreorder \n"
" .set noat \n"
" mfc0 $1, $12 \n"
" andi %[flags], 1 \n"
" ori $1, 0x1f \n"
" xori $1, 0x1f \n"
" or %[flags], $1 \n"
" mtc0 %[flags], $12 \n"
" " __stringify(__irq_disable_hazard) " \n"
" .set pop \n"
: [flags] "=r" (__tmp1)
: "0" (flags)
: "memory");
preempt_enable_notrace();
}
EXPORT_SYMBOL(arch_local_irq_restore);
#endif /* !CONFIG_CPU_HAS_DIEI */