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 f93a1a00f2bd ("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>

MIPS: Make DIEI support as a config option

DI(Disable Interrupt) and EI(Enable Interrupt) instructions is required by
MIPSR2/MIPSR6, however, it appears to be buggy on some processors such as
Loongson-3A1000. Thus we make it as a config option to allow disable it at
compile time with CPU_MIPSR2 selected.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: chenhc@lemote.com
Cc: paul.burton@mips.com
Cc: linux-kernel@vger.kernel.org

MIPS: Cleanup the unused __arch_local_irq_restore() function

In history, __arch_local_irq_restore() is only used by SMTC. However,
SMTC support has been removed since 3.16, this patch remove the unused
function.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12159/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: asm: irqflags: Add MIPS R6 related definitions

Add the MIPS R6 related definitions to the IRQ related macros

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

MIPS: lib: mips-atomic.c: Remove obsolete ifdefery

Having #ifdefs just to guard comments is not really helpful
so drop them. Moreover, the code wasn't really reached anyway
since there is a #ifndef CONFIG_CPU_MIPSR2 on the top of the file.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8513/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: MT: Remove SMTC support

Nobody is maintaining SMTC anymore and there also seems to be no userbase.
Which is a pity - the SMTC technology primarily developed by Kevin D.
Kissell <kevink@paralogos.com> is an ingenious demonstration for the MT
ASE's power and elegance.

Based on Markos Chandras <Markos.Chandras@imgtec.com> patch
https://patchwork.linux-mips.org/patch/6719/ which while very similar did
no longer apply cleanly when I tried to merge it plus some additional
post-SMTC cleanup - SMTC was a feature as tricky to remove as it was to
merge once upon a time.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: Get rid of the use of .macro in C code.

It fails with LTO and probably has always been a fragile.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

MIPS: Fix crash that occurs when function tracing is enabled

A recent patch changed some irq routines from inlines to functions.
These routines are called by the tracer code. Now that they're functions,
if they are compiled for function tracing they will call the tracer
and crash the system due to infinite recursion. The fix disables
tracing in these functions by using "notrace" in the function
definition.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Reviewed-by: David Daney <david.daney@cavium.com>
Pathchwork: https://patchwork.linux-mips.org/patch/4564/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

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>