Author: avg
Date: Tue Jun 26 08:56:34 2018
New Revision: 335658
URL: https://svnweb.freebsd.org/changeset/base/335658
Log:
MFC r333268: for bus suspend, detach and shutdown iterate children in reverse
order
Modified:
stable/11/sys/kern/subr_bus.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/kern/subr_bus.c
==============================================================================
--- stable/11/sys/kern/subr_bus.c Tue Jun 26 08:35:58 2018
(r335657)
+++ stable/11/sys/kern/subr_bus.c Tue Jun 26 08:56:34 2018
(r335658)
@@ -3697,7 +3697,11 @@ bus_generic_detach(device_t dev)
if (dev->state != DS_ATTACHED)
return (EBUSY);
- TAILQ_FOREACH(child, &dev->children, link) {
+ /*
+ * Detach children in the reverse order.
+ * See bus_generic_suspend for details.
+ */
+ TAILQ_FOREACH_REVERSE(child, &dev->children, device_list, link) {
if ((error = device_detach(child)) != 0)
return (error);
}
@@ -3717,7 +3721,11 @@ bus_generic_shutdown(device_t dev)
{
device_t child;
- TAILQ_FOREACH(child, &dev->children, link) {
+ /*
+ * Shut down children in the reverse order.
+ * See bus_generic_suspend for details.
+ */
+ TAILQ_FOREACH_REVERSE(child, &dev->children, device_list, link) {
device_shutdown(child);
}
@@ -3770,15 +3778,23 @@ int
bus_generic_suspend(device_t dev)
{
int error;
- device_t child, child2;
+ device_t child;
- TAILQ_FOREACH(child, &dev->children, link) {
+ /*
+ * Suspend children in the reverse order.
+ * For most buses all children are equal, so the order does not matter.
+ * Other buses, such as acpi, carefully order their child devices to
+ * express implicit dependencies between them. For such buses it is
+ * safer to bring down devices in the reverse order.
+ */
+ TAILQ_FOREACH_REVERSE(child, &dev->children, device_list, link) {
error = BUS_SUSPEND_CHILD(dev, child);
- if (error) {
- for (child2 = TAILQ_FIRST(&dev->children);
- child2 && child2 != child;
- child2 = TAILQ_NEXT(child2, link))
- BUS_RESUME_CHILD(dev, child2);
+ if (error != 0) {
+ child = TAILQ_NEXT(child, link);
+ if (child != NULL) {
+ TAILQ_FOREACH_FROM(child, &dev->children, link)
+ BUS_RESUME_CHILD(dev, child);
+ }
return (error);
}
}
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