X-Git-Url: https://git.karo-electronics.de/?a=blobdiff_plain;f=kernel%2Fcpu.c;fp=kernel%2Fcpu.c;h=63aa50d7ce1efa16f9c29faa97f734f8c5db5d34;hb=955b2fee301c6fc3565e0b3f071236287b06d379;hp=d7f07a2da5a6b6bcc682d39918b3bd97471d9543;hpb=ef5bfcc8f2afb0fa3ee1a38a80bf1b16a9a0d01e;p=karo-tx-linux.git

diff --git a/kernel/cpu.c b/kernel/cpu.c
index d7f07a2da5a6..63aa50d7ce1e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -308,6 +308,23 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 	}
 	smpboot_park_threads(cpu);
 
+	/*
+	 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
+	 * and RCU users of this state to go away such that all new such users
+	 * will observe it.
+	 *
+	 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
+	 * not imply sync_sched(), so explicitly call both.
+	 */
+#ifdef CONFIG_PREEMPT
+	synchronize_sched();
+#endif
+	synchronize_rcu();
+
+	/*
+	 * So now all preempt/rcu users must observe !cpu_active().
+	 */
+
 	err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
 	if (err) {
 		/* CPU didn't die: tell everyone.  Can't complain. */