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authorPeter Zijlstra <peterz@infradead.org>2018-09-11 11:51:27 +0200
committerIngo Molnar <mingo@kernel.org>2018-09-11 20:01:03 +0200
commitcb92173d1f0474784c6171a9d3fdbbca0ee53554 (patch)
tree235d836c029b9c8213897ab723130b1393558db5 /kernel/cpu.c
parent84818af26350c245c8e1994493b7459c0822be5b (diff)
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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: cb538267ea1e ("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>
Diffstat (limited to 'kernel/cpu.c')
-rw-r--r--kernel/cpu.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 0097acec1c71..be4859f07153 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -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);