Commit-ID: cb92173d1f0474784c6171a9d3fdbbca0ee53554
Gitweb: https://git.kernel.org/tip/cb92173d1f0474784c6171a9d3fdbbca0ee53554
Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 11 Sep 2018 11:51:27 +0200
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Tue, 11 Sep 2018 20:01:03 +0200
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 <mi...@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: linux-tip-comm...@vger.kernel.org
Fixes: cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for
_cpuslocked() operations")
Link:
http://lkml.kernel.org/r/20180911095127.gt24...@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
kernel/cpu.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
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);
