Merge branch 'core/speculation' 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 e70a90634b41cd57de7a6fed4d3ff40d24055590..43e741e88691c2993de99c50ad3e4031bac91ec9 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -313,6 +313,15 @@ void cpus_write_unlock(void)
 
 void lockdep_assert_cpus_held(void)
 {
+       /*
+        * We can't have hotplug operations before userspace starts running,
+        * and some init codepaths will knowingly not take the hotplug lock.
+        * This is all valid, so mute lockdep until it makes sense to report
+        * unheld locks.
+        */
+       if (system_state < SYSTEM_RUNNING)
+               return;
+
        percpu_rwsem_assert_held(&cpu_hotplug_lock);
 }
 
@@ -555,6 +564,20 @@ static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
                cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
 }
 
+static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
+{
+       if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
+               return true;
+       /*
+        * When CPU hotplug is disabled, then taking the CPU down is not
+        * possible because takedown_cpu() and the architecture and
+        * subsystem specific mechanisms are not available. So the CPU
+        * which would be completely unplugged again needs to stay around
+        * in the current state.
+        */
+       return st->state <= CPUHP_BRINGUP_CPU;
+}
+
 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                              enum cpuhp_state target)
 {
@@ -565,8 +588,10 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                st->state++;
                ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
                if (ret) {
-                       st->target = prev_state;
-                       undo_cpu_up(cpu, st);
+                       if (can_rollback_cpu(st)) {
+                               st->target = prev_state;
+                               undo_cpu_up(cpu, st);
+                       }
                        break;
                }
        }