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Subject[PATCH 2/2] smp/hotplug,lockdep: Annotate cpuhp_state
After the st->done annotation, lockdep cross-release now complains
about:

CPU0 CPU1 CPU2
cpuhp_up_callbacks: takedown_cpu: cpuhp_thread_fun:

cpuhp_state
irq_lock_sparse()
irq_lock_sparse()
wait_for_completion()
cpuhp_state
complete()

which again spells deadlock, because CPU0 needs to wait for CPU1's
irq_lock_sparse which will wait for CPU2's completion, which in turn
waits for CPU0's cpuhp_state.

Now, this again mixes up and down chains, but now on cpuhp_state.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Byungchul Park <max.byungchul.park@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Mike Galbraith <efault@gmx.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/cpu.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -67,11 +67,14 @@ struct cpuhp_cpu_state {
static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);

#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
-static struct lock_class_key cpuhp_state_key;
+static struct lock_class_key cpuhp_state_up_key;
+#ifdef CONFIG_HOTPLUG_CPU
+static struct lock_class_key cpuhp_state_down_key;
+#endif
static struct lockdep_map cpuhp_state_lock_map =
- STATIC_LOCKDEP_MAP_INIT("cpuhp_state", &cpuhp_state_key);
+ STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_key);
#endif

/**
* cpuhp_step - Hotplug state machine step
* @name: Name of the step
@@ -714,6 +718,8 @@ static int __ref _cpu_down(unsigned int
cpus_write_lock();

lockdep_reinit_st_done();
+ lockdep_init_map(&cpuhp_state_lock_map, "cpuhp_state-down",
+ &cpuhp_state_down_key, 0);

cpuhp_tasks_frozen = tasks_frozen;

@@ -828,6 +834,8 @@ static int _cpu_up(unsigned int cpu, int
cpus_write_lock();

lockdep_reinit_st_done();
+ lockdep_init_map(&cpuhp_state_lock_map, "cpuhp_state-up",
+ &cpuhp_state_up_key, 0);

if (!cpu_present(cpu)) {
ret = -EINVAL;

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