svn commit: r327430 - in head/sys: geom kern

[Colin Percival]

Author: cperciva
Date: Sun Dec 31 09:23:52 2017
New Revision: 327430
URL: https://svnweb.freebsd.org/changeset/base/327430

Log:
  Instrument "boot holds" for the benefit of the TSLOG framework.  These
  are places where the "main thread" of the booting kernel (either the
  thread which later becomes swapper or the thread which later becomes
  init) has to stop and wait for action to take place in another thread
  before continuing.
  
  There are currently three such holds:
  1. The intr_config_hooks SYSINIT waits for hooks registered via the
  config_intrhook_establish function; this allows (typically) devices
  which need interrupts enabled to complete their initialization to do
  so before root is mounted.
  
  2. The g_waitidle function waits for the GEOM event queue to be empty;
  this ensures that all of the disks which have been attached have been
  tasted before we attempt to mount root.
  
  3. The vfs_mountroot_wait function (in addition to calling g_waitidle)
  waits for holds registered via root_mount_hold; among other things, this
  is used by the USB subsystem to ensure that we don't fail to mount root
  if it's located on a USB disk which takes a while to probe.

Modified:
  head/sys/geom/geom_event.c
  head/sys/kern/subr_autoconf.c
  head/sys/kern/vfs_mountroot.c

Modified: head/sys/geom/geom_event.c
==============================================================================
--- head/sys/geom/geom_event.c	Sun Dec 31 09:23:35 2017	(r327429)
+++ head/sys/geom/geom_event.c	Sun Dec 31 09:23:52 2017	(r327430)
@@ -87,9 +87,11 @@ g_waitidle(void)
 	g_topology_assert_not();
 
 	mtx_lock(&g_eventlock);
+	TSWAIT("GEOM events");
 	while (!TAILQ_EMPTY(&g_events))
 		msleep(&g_pending_events, &g_eventlock, PPAUSE,
 		    "g_waitidle", hz/5);
+	TSUNWAIT("GEOM events");
 	mtx_unlock(&g_eventlock);
 	curthread->td_pflags &= ~TDP_GEOM;
 }
@@ -266,6 +268,7 @@ one_event(void)
 	ep->func(ep->arg, 0);
 	g_topology_assert();
 	mtx_lock(&g_eventlock);
+	TSRELEASE("GEOM events");
 	TAILQ_REMOVE(&g_events, ep, events);
 	ep->flag &= ~EV_INPROGRESS;
 	if (ep->flag & EV_WAKEUP) {
@@ -324,6 +327,7 @@ g_cancel_event(void *ref)
 				break;
 			if (ep->ref[n] != ref)
 				continue;
+			TSRELEASE("GEOM events");
 			TAILQ_REMOVE(&g_events, ep, events);
 			ep->func(ep->arg, EV_CANCEL);
 			mtx_assert(&g_eventlock, MA_OWNED);
@@ -367,6 +371,7 @@ g_post_event_x(g_event_t *func, void *arg, int flag, i
 	ep->func = func;
 	ep->arg = arg;
 	mtx_lock(&g_eventlock);
+	TSHOLD("GEOM events");
 	TAILQ_INSERT_TAIL(&g_events, ep, events);
 	mtx_unlock(&g_eventlock);
 	wakeup(&g_wait_event);

Modified: head/sys/kern/subr_autoconf.c
==============================================================================
--- head/sys/kern/subr_autoconf.c	Sun Dec 31 09:23:35 2017	(r327429)
+++ head/sys/kern/subr_autoconf.c	Sun Dec 31 09:23:52 2017	(r327430)
@@ -155,6 +155,7 @@ boot_run_interrupt_driven_config_hooks(void *dummy)
 	run_interrupt_driven_config_hooks();
 
 	/* Block boot processing until all hooks are disestablished. */
+	TSWAIT("config hooks");
 	mtx_lock(&intr_config_hook_lock);
 	warned = 0;
 	while (!TAILQ_EMPTY(&intr_config_hook_list)) {
@@ -168,6 +169,7 @@ boot_run_interrupt_driven_config_hooks(void *dummy)
 		}
 	}
 	mtx_unlock(&intr_config_hook_lock);
+	TSUNWAIT("config hooks");
 }
 
 SYSINIT(intr_config_hooks, SI_SUB_INT_CONFIG_HOOKS, SI_ORDER_FIRST,
@@ -183,6 +185,7 @@ config_intrhook_establish(struct intr_config_hook *hoo
 {
 	struct intr_config_hook *hook_entry;
 
+	TSHOLD("config hooks");
 	mtx_lock(&intr_config_hook_lock);
 	TAILQ_FOREACH(hook_entry, &intr_config_hook_list, ich_links)
 		if (hook_entry == hook)
@@ -239,6 +242,7 @@ config_intrhook_disestablish(struct intr_config_hook *
 	if (next_to_notify == hook)
 		next_to_notify = TAILQ_NEXT(hook, ich_links);
 	TAILQ_REMOVE(&intr_config_hook_list, hook, ich_links);
+	TSRELEASE("config hooks");
 
 	/* Wakeup anyone watching the list */
 	wakeup(&intr_config_hook_list);

Modified: head/sys/kern/vfs_mountroot.c
==============================================================================
--- head/sys/kern/vfs_mountroot.c	Sun Dec 31 09:23:35 2017	(r327429)
+++ head/sys/kern/vfs_mountroot.c	Sun Dec 31 09:23:52 2017	(r327430)
@@ -176,6 +176,7 @@ root_mount_hold(const char *identifier)
 	h = malloc(sizeof *h, M_DEVBUF, M_ZERO | M_WAITOK);
 	h->who = identifier;
 	mtx_lock(&root_holds_mtx);
+	TSHOLD("root mount");
 	LIST_INSERT_HEAD(&root_holds, h, list);
 	mtx_unlock(&root_holds_mtx);
 	return (h);
@@ -190,6 +191,7 @@ root_mount_rel(struct root_hold_token *h)
 
 	mtx_lock(&root_holds_mtx);
 	LIST_REMOVE(h, list);
+	TSRELEASE("root mount");
 	wakeup(&root_holds);
 	mtx_unlock(&root_holds_mtx);
 	free(h, M_DEVBUF);
@@ -956,8 +958,10 @@ vfs_mountroot_wait(void)
 				printf(" %s", h->who);
 			printf("\n");
 		}
+		TSWAIT("root mount");
 		msleep(&root_holds, &root_holds_mtx, PZERO | PDROP, "roothold",
 		    hz);
+		TSUNWAIT("root mount");
 	}
 
 	TSEXIT();