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Message-Id: <20201106103602.9849-3-will@kernel.org>
Date: Fri, 6 Nov 2020 10:36:02 +0000
From: Will Deacon <will@...nel.org>
To: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com,
Will Deacon <will@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Qian Cai <cai@...hat.com>,
"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH 2/2] arm64: smp: Tell RCU about CPUs that fail to come online
Commit ce3d31ad3cac ("arm64/smp: Move rcu_cpu_starting() earlier") ensured
that RCU is informed early about incoming CPUs that might end up calling
into printk() before they are online. However, if such a CPU fails the
early CPU feature compatibility checks in check_local_cpu_capabilities(),
then it will be powered off or parked without informing RCU, leading to
an endless stream of stalls:
| rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
| rcu: 2-O...: (0 ticks this GP) idle=002/1/0x4000000000000000 softirq=0/0 fqs=2593
| (detected by 0, t=5252 jiffies, g=9317, q=136)
| Task dump for CPU 2:
| task:swapper/2 state:R running task stack: 0 pid: 0 ppid: 1 flags:0x00000028
| Call trace:
| ret_from_fork+0x0/0x30
Ensure that the dying CPU invokes rcu_report_dead() prior to being powered
off or parked.
Cc: Qian Cai <cai@...hat.com>
Cc: "Paul E. McKenney" <paulmck@...nel.org>
Suggested-by: Qian Cai <cai@...hat.com>
Signed-off-by: Will Deacon <will@...nel.org>
---
arch/arm64/kernel/smp.c | 1 +
kernel/rcu/tree.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 09c96f57818c..18e9727d3f64 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -413,6 +413,7 @@ void cpu_die_early(void)
/* Mark this CPU absent */
set_cpu_present(cpu, 0);
+ rcu_report_dead(cpu);
if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
update_cpu_boot_status(CPU_KILL_ME);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2a52f42f64b6..bd04b09b84b3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4077,7 +4077,6 @@ void rcu_cpu_starting(unsigned int cpu)
smp_mb(); /* Ensure RCU read-side usage follows above initialization. */
}
-#ifdef CONFIG_HOTPLUG_CPU
/*
* The outgoing function has no further need of RCU, so remove it from
* the rcu_node tree's ->qsmaskinitnext bit masks.
@@ -4117,6 +4116,7 @@ void rcu_report_dead(unsigned int cpu)
rdp->cpu_started = false;
}
+#ifdef CONFIG_HOTPLUG_CPU
/*
* The outgoing CPU has just passed through the dying-idle state, and we
* are being invoked from the CPU that was IPIed to continue the offline
--
2.29.1.341.ge80a0c044ae-goog
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