Commit-ID: cb92173d1f0474784c6171a9d3fdbbca0ee53554 Gitweb: https://git.kernel.org/tip/cb92173d1f0474784c6171a9d3fdbbca0ee53554 Author: Peter Zijlstra <[email protected]> AuthorDate: Tue, 11 Sep 2018 11:51:27 +0200 Committer: Ingo Molnar <[email protected]> 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 <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Fixes: cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- 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);
