Move the loadav() callout into its own kthread since it uses allproc_lock

which is a sleepable lock and thus is not safe to acquire from a callout
routine.

1 files changed, 31 insertions, 12 deletions

diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index a7c8f86..7ddd49b 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -49,6 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/condvar.h>
 #include <sys/kernel.h>
 #include <sys/ktr.h>
+#include <sys/kthread.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/proc.h>
@@ -76,7 +77,6 @@ SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, NULL)
 int	hogticks;
 int	lbolt;
 
-static struct callout loadav_callout;
 static struct callout lbolt_callout;
 
 struct loadavg averunnable =
@@ -96,7 +96,8 @@ static int      fscale __unused = FSCALE;
 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
 
 static void	endtsleep(void *);
-static void	loadav(void *arg);
+static void	loadav(void);
+static void	loadav_thread(void *dummy);
 static void	lboltcb(void *arg);
 
 /*
@@ -581,7 +582,7 @@ setrunnable(struct thread *td)
  * Completely Bogus.. only works with 1:1 (but compiles ok now :-)
  */
 static void
-loadav(void *arg)
+loadav(void)
 {
 	int i, nrun;
 	struct loadavg *avg;
@@ -610,14 +611,31 @@ nextproc:
 	for (i = 0; i < 3; i++)
 		avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
 		    nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
+}
 
-	/*
-	 * Schedule the next update to occur after 5 seconds, but add a
-	 * random variation to avoid synchronisation with processes that
-	 * run at regular intervals.
-	 */
-	callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
-	    loadav, NULL);
+/*
+ * Main loop for a kthread that executes loadav() periodically.
+ */
+static void
+loadav_thread(void *dummy)
+{
+	struct proc *p;
+	int nowake;
+
+	p = curthread->td_proc;
+	PROC_LOCK(p);
+	p->p_flag |= P_NOLOAD;
+	PROC_UNLOCK(p);
+	for (;;) {
+		loadav();
+		/*
+		 * Schedule the next update to occur after 5 seconds, but
+		 * add a random variation to avoid synchronisation with
+		 * processes that run at regular intervals.
+		 */
+		tsleep(&nowake, curthread->td_priority, "-", hz * 4 +
+		    (int)(random() % (hz * 2 + 1)));
+	}
 }
 
 static void
@@ -632,12 +650,13 @@ static void
 synch_setup(dummy)
 	void *dummy;
 {
-	callout_init(&loadav_callout, 0);
 	callout_init(&lbolt_callout, CALLOUT_MPSAFE);
 
 	/* Kick off timeout driven events by calling first time. */
-	loadav(NULL);
 	lboltcb(NULL);
+
+	/* Kick off loadav kernel process. */
+	kthread_create(loadav_thread, NULL, NULL, 0, 0, "loadav");
 }
 
 /*