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locking/lockdep, cpu/hotplug: Annotate AP thread 

Anybody trying to assert the cpu_hotplug_lock is held (lockdep_assert_cpus_held())
from AP callbacks will fail, because the lock is held by the BP.

Stick in an explicit annotation in cpuhp_thread_fun() to make this work.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-tip-commits@vger.kernel.org
Fixes: cb538267ea ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations")
Link: http://lkml.kernel.org/r/20180911095127.GT24082@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2018-09-11 11:51:27 +02:00 committed by Ingo Molnar
parent 84818af263
commit cb92173d1f
1 changed files with 28 additions and 0 deletions
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28
kernel/cpu.c
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@ -315,6 +315,16 @@ void lockdep_assert_cpus_held(void)
percpu_rwsem_assert_held(&cpu_hotplug_lock);
}
static void lockdep_acquire_cpus_lock(void)
{
rwsem_acquire(&cpu_hotplug_lock.rw_sem.dep_map, 0, 0, _THIS_IP_);
}
static void lockdep_release_cpus_lock(void)
{
rwsem_release(&cpu_hotplug_lock.rw_sem.dep_map, 1, _THIS_IP_);
}
/*
* Wait for currently running CPU hotplug operations to complete (if any) and
* disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
@ -344,6 +354,17 @@ void cpu_hotplug_enable(void)
cpu_maps_update_done();
}
EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
#else
static void lockdep_acquire_cpus_lock(void)
{
}
static void lockdep_release_cpus_lock(void)
{
}
#endif /* CONFIG_HOTPLUG_CPU */
#ifdef CONFIG_HOTPLUG_SMT
@ -616,6 +637,12 @@ static void cpuhp_thread_fun(unsigned int cpu)
*/
smp_mb();
/*
* The BP holds the hotplug lock, but we're now running on the AP,
* ensure that anybody asserting the lock is held, will actually find
* it so.
*/
lockdep_acquire_cpus_lock();
cpuhp_lock_acquire(bringup);
if (st->single) {
@ -661,6 +688,7 @@ static void cpuhp_thread_fun(unsigned int cpu)
}
cpuhp_lock_release(bringup);
lockdep_release_cpus_lock();
if (!st->should_run)
complete_ap_thread(st, bringup);