svn commit: r216087 - stable/8/sys/kern

[Justin T. Gibbs]

Author: gibbs
Date: Tue Nov 30 22:25:44 2010
New Revision: 216087
URL: http://svn.freebsd.org/changeset/base/216087

Log:
  Merge revision 211236 form current:
  
  Allow interrupt driven config hooks to be registered from config hook callbacks.
  
  Interrupt driven configuration hooks serve two purposes: they are a
  mechanism for registering for a callback that is invoked once interrupt
  services are available, and they hold off root device selection so long
  as any configuration hooks are still active.  Before this change, it was
  not possible to safely register additional hooks from the context of a
  configuration hook callback.  The need for this feature arises when
  interrupts are required to discover new devices (e.g. access to the XenStore
  to find para-virtualized devices) which in turn also require the ability
  to hold off root device selection until some lengthy, interrupt driven,
  configuration task has completed (e.g. Xen front/back device driver
  negotiation).
  
  More specifically, the mutex protecting the list of active configuration
  hooks is never held during a callback, and static information is used
  to ensure proper ordering and only a single callback to each hook even
  when faced with registration or removal of a hook during an active run.
  
  Sponsored by:	Spectra Logic Corporation
  Approved by:	re (kib)

Modified:
  stable/8/sys/kern/subr_autoconf.c
Directory Properties:
  stable/8/sys/   (props changed)

Modified: stable/8/sys/kern/subr_autoconf.c
==============================================================================
--- stable/8/sys/kern/subr_autoconf.c	Tue Nov 30 21:26:21 2010	(r216086)
+++ stable/8/sys/kern/subr_autoconf.c	Tue Nov 30 22:25:44 2010	(r216087)
@@ -55,11 +55,12 @@ __FBSDID("$FreeBSD$");
  */
 static TAILQ_HEAD(, intr_config_hook) intr_config_hook_list =
 	TAILQ_HEAD_INITIALIZER(intr_config_hook_list);
+static struct intr_config_hook *next_to_notify;
 static struct mtx intr_config_hook_lock;
 MTX_SYSINIT(intr_config_hook, &intr_config_hook_lock, "intr config", MTX_DEF);
 
 /* ARGSUSED */
-static void run_interrupt_driven_config_hooks(void *dummy);
+static void run_interrupt_driven_config_hooks(void);
 
 /*
  * If we wait too long for an interrupt-driven config hook to return, print
@@ -91,19 +92,46 @@ run_interrupt_driven_config_hooks_warnin
 }
 
 static void
-run_interrupt_driven_config_hooks(void *dummy)
+run_interrupt_driven_config_hooks()
 {
-	struct intr_config_hook *hook_entry, *next_entry;
-	int warned;
+	static int running;
+	struct intr_config_hook *hook_entry;
 
 	mtx_lock(&intr_config_hook_lock);
-	TAILQ_FOREACH_SAFE(hook_entry, &intr_config_hook_list, ich_links,
-	    next_entry) {
+
+	/*
+	 * If hook processing is already active, any newly
+	 * registered hooks will eventually be notified.
+	 * Let the currently running session issue these
+	 * notifications.
+	 */
+	if (running != 0) {
+		mtx_unlock(&intr_config_hook_lock);
+		return;
+	}
+	running = 1;
+
+	while (next_to_notify != NULL) {
+		hook_entry = next_to_notify;
+		next_to_notify = TAILQ_NEXT(hook_entry, ich_links);
 		mtx_unlock(&intr_config_hook_lock);
 		(*hook_entry->ich_func)(hook_entry->ich_arg);
 		mtx_lock(&intr_config_hook_lock);
 	}
 
+	running = 0;
+	mtx_unlock(&intr_config_hook_lock);
+}
+
+static void
+boot_run_interrupt_driven_config_hooks(void *dummy)
+{
+	int warned;
+
+	run_interrupt_driven_config_hooks();
+
+	/* Block boot processing until all hooks are disestablished. */
+	mtx_lock(&intr_config_hook_lock);
 	warned = 0;
 	while (!TAILQ_EMPTY(&intr_config_hook_list)) {
 		if (msleep(&intr_config_hook_list, &intr_config_hook_lock,
@@ -117,8 +145,9 @@ run_interrupt_driven_config_hooks(void *
 	}
 	mtx_unlock(&intr_config_hook_lock);
 }
+
 SYSINIT(intr_config_hooks, SI_SUB_INT_CONFIG_HOOKS, SI_ORDER_FIRST,
-	run_interrupt_driven_config_hooks, NULL);
+	boot_run_interrupt_driven_config_hooks, NULL);
 
 /*
  * Register a hook that will be called after "cold"
@@ -141,10 +170,16 @@ config_intrhook_establish(struct intr_co
 		return (1);
 	}
 	TAILQ_INSERT_TAIL(&intr_config_hook_list, hook, ich_links);
+	if (next_to_notify == NULL)
+		next_to_notify = hook;
 	mtx_unlock(&intr_config_hook_lock);
 	if (cold == 0)
+		/*
+		 * XXX Call from a task since not all drivers expect
+		 *     to be re-entered at the time a hook is established.
+		 */
 		/* XXX Sufficient for modules loaded after initial config??? */
-		run_interrupt_driven_config_hooks(NULL);	
+		run_interrupt_driven_config_hooks();	
 	return (0);
 }
 
@@ -161,6 +196,8 @@ config_intrhook_disestablish(struct intr
 		panic("config_intrhook_disestablish: disestablishing an "
 		      "unestablished hook");
 
+	if (next_to_notify == hook)
+		next_to_notify = TAILQ_NEXT(hook, ich_links);
 	TAILQ_REMOVE(&intr_config_hook_list, hook, ich_links);
 
 	/* Wakeup anyone watching the list */