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authorWill Deacon <will@kernel.org>2020-11-06 10:25:49 +0000
committerWill Deacon <will@kernel.org>2020-11-10 13:11:44 +0000
commit04e613ded8c26489b3e0f9101b44462f780d1a35 (patch)
tree1dd103a5013da84ee4d8ab4f96f14b5285d80b06
parent891deb87585017d526b67b59c15d38755b900fea (diff)
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@redhat.com> Cc: "Paul E. McKenney" <paulmck@kernel.org> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Suggested-by: Qian Cai <cai@redhat.com> Link: https://lore.kernel.org/r/20201105222242.GA8842@willie-the-truck Link: https://lore.kernel.org/r/20201106103602.9849-3-will@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
-rw-r--r--arch/arm64/kernel/smp.c1
-rw-r--r--kernel/rcu/tree.c2
2 files changed, 2 insertions, 1 deletions
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 06895ef85d69..946e7c0c4cf7 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