Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

[sfrench/cifs-2.6.git] / kernel / cpu.c

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 2fb49916ea560735d7f51f8a7610892303ec243a..3c7f3b4c453cf57c8e37dd5fadc9f5941f074f0d 100644 (file)
--- 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
@@ -362,6 +383,7 @@ void __init cpu_smt_disable(bool force)
                pr_info("SMT: Force disabled\n");
                cpu_smt_control = CPU_SMT_FORCE_DISABLED;
        } else {
+               pr_info("SMT: disabled\n");
                cpu_smt_control = CPU_SMT_DISABLED;
        }
 }
@@ -607,15 +629,21 @@ static void cpuhp_thread_fun(unsigned int cpu)
        bool bringup = st->bringup;
        enum cpuhp_state state;
 
+       if (WARN_ON_ONCE(!st->should_run))
+               return;
+
        /*
         * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
         * that if we see ->should_run we also see the rest of the state.
         */
        smp_mb();
 
-       if (WARN_ON_ONCE(!st->should_run))
-               return;
-
+       /*
+        * 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 +689,7 @@ 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);
@@ -916,7 +945,8 @@ static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
                if (ret) {
                        st->target = prev_state;
-                       undo_cpu_down(cpu, st);
+                       if (st->state < prev_state)
+                               undo_cpu_down(cpu, st);
                        break;
                }
        }
@@ -969,7 +999,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
         * to do the further cleanups.
         */
        ret = cpuhp_down_callbacks(cpu, st, target);
-       if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
+       if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
                cpuhp_reset_state(st, prev_state);
                __cpuhp_kick_ap(st);
        }