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From: Guo Ren <guoren@kernel.org>
To: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu,
	alex@ghiti.fr, samuel.holland@sifive.com, tglx@kernel.org,
	bigeasy@linutronix.de
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>,
	stable@vger.kernel.org, Huacai Chen <chenhuacai@loongson.cn>,
	Jonas Jelonek <jelonek.jonas@gmail.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Jiayuan Chen <jiayuan.chen@linux.dev>
Subject: [PATCH] riscv: Report dying CPU to RCU in IPI_CPU_STOP
Date: Mon, 22 Jun 2026 13:40:18 +0000	[thread overview]
Message-ID: <20260622134018.817508-1-guoren@kernel.org> (raw)

From: "Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>

This is a port of MIPS commit 9f3f3bdc6d9dac1 ("MIPS: smp: report
dying CPU to RCU in stop_this_cpu()") inspired by the Loongarch
mailing thread.

The smp_send_stop() parks all secondary CPUs in IPI_CPU_STOP, which
marks the CPU offline for the scheduler via set_cpu_online(false),
but never informs RCU, so RCU keeps expecting a quiescent state
from CPUs that are now spinning forever with interrupts disabled.

Please read the MIPS commit mentioned before for details.

Cc: stable@vger.kernel.org
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Jonas Jelonek <jelonek.jonas@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: Thomas Gleixner <tglx@kernel.org>
Fixes: 91840be8f710 ("irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT")
Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
---
 arch/riscv/kernel/smp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index fa66f9c97d74..0a73b36be825 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -82,6 +82,7 @@ int riscv_hartid_to_cpuid(unsigned long hartid)
 static void ipi_stop(void)
 {
 	set_cpu_online(smp_processor_id(), false);
+	rcutree_report_cpu_dead();
 	while (1)
 		wait_for_interrupt();
 }
-- 
2.43.0


WARNING: multiple messages have this Message-ID (diff)
From: Guo Ren <guoren@kernel.org>
To: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu,
	alex@ghiti.fr, samuel.holland@sifive.com, tglx@kernel.org,
	bigeasy@linutronix.de
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>,
	stable@vger.kernel.org, Huacai Chen <chenhuacai@loongson.cn>,
	Jonas Jelonek <jelonek.jonas@gmail.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Jiayuan Chen <jiayuan.chen@linux.dev>
Subject: [PATCH] riscv: Report dying CPU to RCU in IPI_CPU_STOP
Date: Mon, 22 Jun 2026 13:40:18 +0000	[thread overview]
Message-ID: <20260622134018.817508-1-guoren@kernel.org> (raw)

From: "Guo Ren (Alibaba DAMO Academy)" <guoren@kernel.org>

This is a port of MIPS commit 9f3f3bdc6d9dac1 ("MIPS: smp: report
dying CPU to RCU in stop_this_cpu()") inspired by the Loongarch
mailing thread.

The smp_send_stop() parks all secondary CPUs in IPI_CPU_STOP, which
marks the CPU offline for the scheduler via set_cpu_online(false),
but never informs RCU, so RCU keeps expecting a quiescent state
from CPUs that are now spinning forever with interrupts disabled.

Please read the MIPS commit mentioned before for details.

Cc: stable@vger.kernel.org
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Jonas Jelonek <jelonek.jonas@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: Thomas Gleixner <tglx@kernel.org>
Fixes: 91840be8f710 ("irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT")
Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
---
 arch/riscv/kernel/smp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index fa66f9c97d74..0a73b36be825 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -82,6 +82,7 @@ int riscv_hartid_to_cpuid(unsigned long hartid)
 static void ipi_stop(void)
 {
 	set_cpu_online(smp_processor_id(), false);
+	rcutree_report_cpu_dead();
 	while (1)
 		wait_for_interrupt();
 }
-- 
2.43.0


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             reply	other threads:[~2026-06-22 13:41 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-06-22 13:40 Guo Ren [this message]
2026-06-22 13:40 ` [PATCH] riscv: Report dying CPU to RCU in IPI_CPU_STOP Guo Ren

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