X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=blobdiff_plain;f=kernel%2Fcpu.c;h=43e741e88691c2993de99c50ad3e4031bac91ec9;hp=e70a90634b41cd57de7a6fed4d3ff40d24055590;hb=cbafee55b5a0ec47baac622bce6b4d19afe45576;hpb=0336e04a6520bdaefdb0769d2a70084fa52e81ed

diff --git a/kernel/cpu.c b/kernel/cpu.c
index e70a90634b41..43e741e88691 100644
--- 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;
 		}
 	}