Commit-ID: f1b2f6eccf99fc457221cc84c7550a8e3b17d4df
Gitweb: https://git.kernel.org/tip/f1b2f6eccf99fc457221cc84c7550a8e3b17d4df
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 11 Sep 2018 11:51:27 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 11 Sep 2018 12:37:00 +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 <mingo@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-tip-commits@xxxxxxxxxxxxxxx
Fixes: cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations")
Link: http://lkml.kernel.org/r/20180911095127.GT24082@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/cpu.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 0097acec1c71..08c168b159da 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -616,6 +616,12 @@ 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.
+ */
+ rwsem_acquire(&cpu_hotplug_lock.rw_sem.dep_map, 0, 0, _THIS_IP_);
cpuhp_lock_acquire(bringup);
if (st->single) {
@@ -661,6 +667,7 @@ static void cpuhp_thread_fun(unsigned int cpu)
}
cpuhp_lock_release(bringup);
+ rwsem_release(&cpu_hotplug_lock.rw_sem.dep_map, 1, _THIS_IP_);
if (!st->should_run)
complete_ap_thread(st, bringup);
|