If we're on an SMP kernel and there is more than 1 CPU, reject any attempts

to change the freq before the other CPUs are active.  The current code
always attempts to change all CPUs to match each other, and the requisite
sched_bind() call won't work before APs are launched.

1 files changed, 17 insertions, 1 deletions

diff --git a/sys/kern/kern_cpu.c b/sys/kern/kern_cpu.c
index c72ead6..8320ee4 100644
--- a/sys/kern/kern_cpu.c
+++ b/sys/kern/kern_cpu.c
@@ -37,10 +37,11 @@ __FBSDID("$FreeBSD$");
 #include <sys/module.h>
 #include <sys/proc.h>
 #include <sys/queue.h>
+#include <sys/sbuf.h>
 #include <sys/sched.h>
+#include <sys/smp.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>
-#include <sys/sbuf.h>
 #include <sys/sx.h>
 #include <sys/timetc.h>
 #include <sys/taskqueue.h>
@@ -243,6 +244,21 @@ cf_set_method(device_t dev, const struct cf_level *level, int priority)
 
 	CF_MTX_LOCK(&sc->lock);
 
+#ifdef SMP
+	/*
+	 * If still booting and secondary CPUs not started yet, don't allow
+	 * changing the frequency until they're online.  This is because we
+	 * can't switch to them using sched_bind() and thus we'd only be
+	 * switching the main CPU.  XXXTODO: Need to think more about how to
+	 * handle having different CPUs at different frequencies.  
+	 */
+	if (mp_ncpus > 1 && !smp_active) {
+		device_printf(dev, "rejecting change, SMP not started yet\n");
+		error = ENXIO;
+		goto out;
+	}
+#endif /* SMP */
+
 	/*
 	 * If the requested level has a lower priority, don't allow
 	 * the new level right now.