[PATCH 0/2] Add HARDLOCKUP_DETECTOR_PERF for riscv

[PATCH 0/2] Add HARDLOCKUP_DETECTOR_PERF for riscv

[Yunhui Cui]

This patchset is mainly based on RISCV_SSE, and the enabling of the
hardlockup perf feature depends on RISCV_PMU_SSE.
Link: https://lore.kernel.org/all/20250808153901.2477005-1-cleger@rivosinc.com/
patch[1]: Move watchdog_hld.c to kernel/ to facilitate reuse by RISC-V.
patch[2]: Add Kconfig selections for RISC-V.

Yunhui Cui (2):
  watchdog: refactor watchdog_hld functionality
  riscv: add HARDLOCKUP_DETECTOR_PERF support

 arch/arm64/kernel/Makefile                   | 1 -
 arch/riscv/Kconfig                           | 3 +++
 drivers/perf/arm_pmu.c                       | 2 +-
 drivers/perf/riscv_pmu_sbi.c                 | 8 ++++++++
 include/linux/nmi.h                          | 1 +
 include/linux/perf/arm_pmu.h                 | 2 --
 kernel/Makefile                              | 2 +-
 {arch/arm64/kernel => kernel}/watchdog_hld.c | 8 ++++++--
 8 files changed, 20 insertions(+), 7 deletions(-)
 rename {arch/arm64/kernel => kernel}/watchdog_hld.c (97%)

-- 
2.39.5

[PATCH 1/2] watchdog: refactor watchdog_hld functionality

[Yunhui Cui]

Move watchdog_hld.c to kernel/, and rename arm_pmu_irq_is_nmi()
to arch_pmu_irq_is_nmi() for cross-arch reusability.

Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
---
 arch/arm64/kernel/Makefile                   | 1 -
 drivers/perf/arm_pmu.c                       | 2 +-
 include/linux/nmi.h                          | 1 +
 include/linux/perf/arm_pmu.h                 | 2 --
 kernel/Makefile                              | 2 +-
 {arch/arm64/kernel => kernel}/watchdog_hld.c | 8 ++++++--
 6 files changed, 9 insertions(+), 7 deletions(-)
 rename {arch/arm64/kernel => kernel}/watchdog_hld.c (97%)

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 76f32e424065e..12d77f373fea4 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -44,7 +44,6 @@ obj-$(CONFIG_KUSER_HELPERS)		+= kuser32.o
 obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o entry-ftrace.o
 obj-$(CONFIG_MODULES)			+= module.o module-plts.o
 obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o perf_callchain.o
-obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF)	+= watchdog_hld.o
 obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
 obj-$(CONFIG_CPU_PM)			+= sleep.o suspend.o
 obj-$(CONFIG_KGDB)			+= kgdb.o
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 5c310e803dd78..4fd7f88d44543 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -696,7 +696,7 @@ static int armpmu_get_cpu_irq(struct arm_pmu *pmu, int cpu)
 	return per_cpu(hw_events->irq, cpu);
 }
 
-bool arm_pmu_irq_is_nmi(void)
+bool arch_pmu_irq_is_nmi(void)
 {
 	return has_nmi;
 }
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index cf3c6ab408aac..c34bdc4f43f6d 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -207,6 +207,7 @@ static inline bool trigger_single_cpu_backtrace(int cpu)
 #ifdef CONFIG_HARDLOCKUP_DETECTOR_PERF
 u64 hw_nmi_get_sample_period(int watchdog_thresh);
 bool arch_perf_nmi_is_available(void);
+bool arch_pmu_irq_is_nmi(void);
 #endif
 
 #if defined(CONFIG_HARDLOCKUP_CHECK_TIMESTAMP) && \
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index 93c9a26492fcf..6b53fb453fd63 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -184,8 +184,6 @@ void kvm_host_pmu_init(struct arm_pmu *pmu);
 #define kvm_host_pmu_init(x)	do { } while(0)
 #endif
 
-bool arm_pmu_irq_is_nmi(void);
-
 /* Internal functions only for core arm_pmu code */
 struct arm_pmu *armpmu_alloc(void);
 void armpmu_free(struct arm_pmu *pmu);
diff --git a/kernel/Makefile b/kernel/Makefile
index c60623448235f..4ec7702b00aa1 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -101,7 +101,7 @@ obj-$(CONFIG_KGDB) += debug/
 obj-$(CONFIG_DETECT_HUNG_TASK) += hung_task.o
 obj-$(CONFIG_LOCKUP_DETECTOR) += watchdog.o
 obj-$(CONFIG_HARDLOCKUP_DETECTOR_BUDDY) += watchdog_buddy.o
-obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_perf.o
+obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_perf.o watchdog_hld.o
 obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RELAY) += relay.o
 obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
diff --git a/arch/arm64/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
similarity index 97%
rename from arch/arm64/kernel/watchdog_hld.c
rename to kernel/watchdog_hld.c
index 3093037dcb7be..f3864e604a6b5 100644
--- a/arch/arm64/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/nmi.h>
 #include <linux/cpufreq.h>
-#include <linux/perf/arm_pmu.h>
 
 /*
  * Safe maximum CPU frequency in case a particular platform doesn't implement
@@ -25,6 +24,11 @@ u64 hw_nmi_get_sample_period(int watchdog_thresh)
 	return (u64)max_cpu_freq * watchdog_thresh;
 }
 
+__weak bool arch_pmu_irq_is_nmi(void)
+{
+	return false;
+}
+
 bool __init arch_perf_nmi_is_available(void)
 {
 	/*
@@ -32,7 +36,7 @@ bool __init arch_perf_nmi_is_available(void)
 	 * however, the pmu interrupts will act like a normal interrupt instead of
 	 * NMI and the hardlockup detector would be broken.
 	 */
-	return arm_pmu_irq_is_nmi();
+	return arch_pmu_irq_is_nmi();
 }
 
 static int watchdog_perf_update_period(void *data)
-- 
2.39.5

[PATCH 2/2] riscv: add HARDLOCKUP_DETECTOR_PERF support

[Yunhui Cui]

Reuse watchdog_hld.c to enable HARDLOCKUP_DETECTOR_PERF and
add Kconfig selections for RISC-V.

Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
---
 arch/riscv/Kconfig           | 3 +++
 drivers/perf/riscv_pmu_sbi.c | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 451eb23d86c96..214b1ead5781a 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -184,6 +184,9 @@ config RISCV
 	select HAVE_PAGE_SIZE_4KB
 	select HAVE_PCI
 	select HAVE_PERF_EVENTS
+	select PERF_EVENTS
+	select HAVE_PERF_EVENTS_NMI if RISCV_SSE && RISCV_PMU_SSE
+	select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && HAVE_PERF_EVENTS_NMI
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
 	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 8c1ac7985df6c..c5423a046d016 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -22,6 +22,7 @@
 #include <linux/sched/clock.h>
 #include <linux/soc/andes/irq.h>
 #include <linux/workqueue.h>
+#include <linux/nmi.h>
 
 #include <asm/errata_list.h>
 #include <asm/sbi.h>
@@ -1102,6 +1103,11 @@ static int pmu_sbi_setup_sse(struct riscv_pmu *pmu)
 }
 #endif
 
+bool arch_pmu_irq_is_nmi(void)
+{
+	return IS_ENABLED(CONFIG_RISCV_PMU_SSE);
+}
+
 static int pmu_sbi_starting_cpu(unsigned int cpu, struct hlist_node *node)
 {
 	struct riscv_pmu *pmu = hlist_entry_safe(node, struct riscv_pmu, node);
@@ -1525,6 +1531,8 @@ static int __init pmu_sbi_devinit(void)
 	/* Notify legacy implementation that SBI pmu is available*/
 	riscv_pmu_legacy_skip_init();
 
+	lockup_detector_retry_init();
+
 	return ret;
 }
 device_initcall(pmu_sbi_devinit)
-- 
2.39.5

Re: [PATCH 1/2] watchdog: refactor watchdog_hld functionality

[Doug Anderson]

Hi,

On Wed, Aug 27, 2025 at 3:10 AM Yunhui Cui <cuiyunhui@bytedance.com> wrote:
>
> Move watchdog_hld.c to kernel/, and rename arm_pmu_irq_is_nmi()
> to arch_pmu_irq_is_nmi() for cross-arch reusability.
>
> Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
> ---
>  arch/arm64/kernel/Makefile                   | 1 -
>  drivers/perf/arm_pmu.c                       | 2 +-
>  include/linux/nmi.h                          | 1 +
>  include/linux/perf/arm_pmu.h                 | 2 --
>  kernel/Makefile                              | 2 +-
>  {arch/arm64/kernel => kernel}/watchdog_hld.c | 8 ++++++--
>  6 files changed, 9 insertions(+), 7 deletions(-)
>  rename {arch/arm64/kernel => kernel}/watchdog_hld.c (97%)

I'm not a huge fan of the perf hardlockup detector and IMO we should
maybe just delete it. Thus spreading it to support a new architecture
isn't my favorite thing to do. Can't you use the buddy hardlockup
detector?

That being said, I did a quick look at your patch. I'm pretty sure you
can't just move the arm64 "watchdog_hld.c" to be generic. Won't
hw_nmi_get_sample_period() conflict with everyone else's (x86 and
powerpc)?

-Doug

Re: [External] Re: [PATCH 1/2] watchdog: refactor watchdog_hld functionality

[yunhui cui]

Hi Doug,

On Sat, Aug 30, 2025 at 5:34 AM Doug Anderson <dianders@chromium.org> wrote:
>
> Hi,
>
> On Wed, Aug 27, 2025 at 3:10 AM Yunhui Cui <cuiyunhui@bytedance.com> wrote:
> >
> > Move watchdog_hld.c to kernel/, and rename arm_pmu_irq_is_nmi()
> > to arch_pmu_irq_is_nmi() for cross-arch reusability.
> >
> > Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
> > ---
> >  arch/arm64/kernel/Makefile                   | 1 -
> >  drivers/perf/arm_pmu.c                       | 2 +-
> >  include/linux/nmi.h                          | 1 +
> >  include/linux/perf/arm_pmu.h                 | 2 --
> >  kernel/Makefile                              | 2 +-
> >  {arch/arm64/kernel => kernel}/watchdog_hld.c | 8 ++++++--
> >  6 files changed, 9 insertions(+), 7 deletions(-)
> >  rename {arch/arm64/kernel => kernel}/watchdog_hld.c (97%)
>
> I'm not a huge fan of the perf hardlockup detector and IMO we should
> maybe just delete it. Thus spreading it to support a new architecture
> isn't my favorite thing to do. Can't you use the buddy hardlockup
> detector?

Why is there a plan to remove CONFIG_HARDLOCKUP_DETECTOR_PERF? Could
you explain the specific reasons? Is the community's future plan to
favor CONFIG_HARDLOCKUP_DETECTOR_BUDDY?

>
> That being said, I did a quick look at your patch. I'm pretty sure you
> can't just move the arm64 "watchdog_hld.c" to be generic. Won't
> hw_nmi_get_sample_period() conflict with everyone else's (x86 and
> powerpc)?
>
> -Doug
>

Thanks,
Yunhui

Re: [External] Re: [PATCH 1/2] watchdog: refactor watchdog_hld functionality

[Doug Anderson]

Hi,

On Sun, Aug 31, 2025 at 10:57 PM yunhui cui <cuiyunhui@bytedance.com> wrote:
>
> Hi Doug,
>
> On Sat, Aug 30, 2025 at 5:34 AM Doug Anderson <dianders@chromium.org> wrote:
> >
> > Hi,
> >
> > On Wed, Aug 27, 2025 at 3:10 AM Yunhui Cui <cuiyunhui@bytedance.com> wrote:
> > >
> > > Move watchdog_hld.c to kernel/, and rename arm_pmu_irq_is_nmi()
> > > to arch_pmu_irq_is_nmi() for cross-arch reusability.
> > >
> > > Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
> > > ---
> > >  arch/arm64/kernel/Makefile                   | 1 -
> > >  drivers/perf/arm_pmu.c                       | 2 +-
> > >  include/linux/nmi.h                          | 1 +
> > >  include/linux/perf/arm_pmu.h                 | 2 --
> > >  kernel/Makefile                              | 2 +-
> > >  {arch/arm64/kernel => kernel}/watchdog_hld.c | 8 ++++++--
> > >  6 files changed, 9 insertions(+), 7 deletions(-)
> > >  rename {arch/arm64/kernel => kernel}/watchdog_hld.c (97%)
> >
> > I'm not a huge fan of the perf hardlockup detector and IMO we should
> > maybe just delete it. Thus spreading it to support a new architecture
> > isn't my favorite thing to do. Can't you use the buddy hardlockup
> > detector?
>
> Why is there a plan to remove CONFIG_HARDLOCKUP_DETECTOR_PERF? Could
> you explain the specific reasons? Is the community's future plan to
> favor CONFIG_HARDLOCKUP_DETECTOR_BUDDY?

I don't think there are any concrete plans, but there was some discussion here:

https://lore.kernel.org/all/CAD=FV=WWUiCi6bZCs_gseFpDDWNkuJMoL6XCftEo6W7q6jRCkg@mail.gmail.com/

-Doug

Re: [External] Re: [PATCH 1/2] watchdog: refactor watchdog_hld functionality

[yunhui cui]

Hi Doug，

On Wed, Sep 3, 2025 at 1:04 AM Doug Anderson <dianders@chromium.org> wrote:
>
> Hi,
>
> On Sun, Aug 31, 2025 at 10:57 PM yunhui cui <cuiyunhui@bytedance.com> wrote:
> >
> > Hi Doug,
> >
> > On Sat, Aug 30, 2025 at 5:34 AM Doug Anderson <dianders@chromium.org> wrote:
> > >
> > > Hi,
> > >
> > > On Wed, Aug 27, 2025 at 3:10 AM Yunhui Cui <cuiyunhui@bytedance.com> wrote:
> > > >
> > > > Move watchdog_hld.c to kernel/, and rename arm_pmu_irq_is_nmi()
> > > > to arch_pmu_irq_is_nmi() for cross-arch reusability.
> > > >
> > > > Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
> > > > ---
> > > >  arch/arm64/kernel/Makefile                   | 1 -
> > > >  drivers/perf/arm_pmu.c                       | 2 +-
> > > >  include/linux/nmi.h                          | 1 +
> > > >  include/linux/perf/arm_pmu.h                 | 2 --
> > > >  kernel/Makefile                              | 2 +-
> > > >  {arch/arm64/kernel => kernel}/watchdog_hld.c | 8 ++++++--
> > > >  6 files changed, 9 insertions(+), 7 deletions(-)
> > > >  rename {arch/arm64/kernel => kernel}/watchdog_hld.c (97%)
> > >
> > > I'm not a huge fan of the perf hardlockup detector and IMO we should
> > > maybe just delete it. Thus spreading it to support a new architecture
> > > isn't my favorite thing to do. Can't you use the buddy hardlockup
> > > detector?
> >
> > Why is there a plan to remove CONFIG_HARDLOCKUP_DETECTOR_PERF? Could
> > you explain the specific reasons? Is the community's future plan to
> > favor CONFIG_HARDLOCKUP_DETECTOR_BUDDY?
>
> I don't think there are any concrete plans, but there was some discussion here:
>
> https://lore.kernel.org/all/CAD=FV=WWUiCi6bZCs_gseFpDDWNkuJMoL6XCftEo6W7q6jRCkg@mail.gmail.com/
>
> -Doug
>

I’ve read your linked content, which details the pros and cons of perf
watchdog and buddy watchdog.
I think everyone will agree on choosing one as the default.
It seems there’s no kernel/watchdog entry in MAINTAINERS—what’s next
for these two approaches?

Thanks,
Yunhui