Re: [PATCH openEuler-21.03] MIPS: Fix kernel hang under FUNCTION_GRAPH_TRACER and PREEMPT_TRACER

Reviewed-by: Cheng Jian cj.chengjian@huawei.com

在 2021/10/16 23:06, jack 写道:

From: Tiezhu Yang yangtiezhu@loongson.cn

stable inclusion from stable-v5.10.44 commit 7519ece673e300b0362572edbde7e030552705ec bugzilla:https://bugzilla.openeuler.org/show_bug.cgi?id=417 CVE: NA

---

[ Upstream commit 78cf0eb926cb1abeff2106bae67752e032fe5f3e ]

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 Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: jack 18380124974@163.com

---

arch/mips/lib/mips-atomic.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/mips/lib/mips-atomic.c b/arch/mips/lib/mips-atomic.c index de03838b343b..a9b72eacfc0b 100644 --- a/arch/mips/lib/mips-atomic.c +++ b/arch/mips/lib/mips-atomic.c @@ -37,7 +37,7 @@ */ notrace void arch_local_irq_disable(void) {

• preempt_disable();

• preempt_disable_notrace();

  __asm__ __volatile__( " .set push \n"

@@ -53,7 +53,7 @@ notrace void arch_local_irq_disable(void) : /* no inputs */ : "memory");

• preempt_enable();

• preempt_enable_notrace(); } EXPORT_SYMBOL(arch_local_irq_disable);

@@ -61,7 +61,7 @@ notrace unsigned long arch_local_irq_save(void) { unsigned long flags;

• preempt_disable();

• preempt_disable_notrace();

  __asm__ __volatile__( " .set push \n"

@@ -78,7 +78,7 @@ notrace unsigned long arch_local_irq_save(void) : /* no inputs */ : "memory");

• preempt_enable();

• preempt_enable_notrace();

  return flags; }

@@ -88,7 +88,7 @@ notrace void arch_local_irq_restore(unsigned long flags) { unsigned long __tmp1;

• preempt_disable();

• preempt_disable_notrace();

  __asm__ __volatile__( " .set push \n"

@@ -106,7 +106,7 @@ notrace void arch_local_irq_restore(unsigned long flags) : "0" (flags) : "memory");

• preempt_enable();

• preempt_enable_notrace(); } EXPORT_SYMBOL(arch_local_irq_restore);