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Add eventhandler notifications for newbus device attach/detach.

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The detach case is slightly complicated by the fact that some in-kernel
consumers may want to know before a device detaches (so they can release
related resources, stop using the device, etc), but the detach can fail. So
there are pre- and post-detach notifications for those consumers who need to
handle all cases.

A couple salient comments from the review, they amount to some helpful
documentation about these events, but there's currently no good place for
such documentation...

Note that in the current newbus locking model, DETACH_BEGIN and
DETACH_COMPLETE/FAILED sequence of event handler invocation might interweave
with other attach/detach events arbitrarily. The handlers should be prepared
for such situations.

Also should note that detach may be called after the parent bus knows the
hardware has left the building. In-kernel consumers have to be prepared to
cope with this race.

Differential Revision:	https://reviews.freebsd.org/D12557
This commit is contained in:
ian 2017-10-08 17:33:49 +00:00
parent 4462f97f62
commit 5cc2194826
2 changed files with 18 additions and 1 deletions
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8
sys/kern/subr_bus.c
View File

@ -2936,6 +2936,7 @@ device_attach(device_t dev)
else
dev->state = DS_ATTACHED;
dev->flags &= ~DF_DONENOMATCH;
EVENTHANDLER_INVOKE(device_attach, dev);
devadded(dev);
return (0);
}
@ -2969,8 +2970,13 @@ device_detach(device_t dev)
if (dev->state != DS_ATTACHED)
return (0);
if ((error = DEVICE_DETACH(dev)) != 0)
EVENTHANDLER_INVOKE(device_detach, dev, EVHDEV_DETACH_BEGIN);
if ((error = DEVICE_DETACH(dev)) != 0) {
EVENTHANDLER_INVOKE(device_detach, dev, EVHDEV_DETACH_FAILED);
return (error);
} else {
EVENTHANDLER_INVOKE(device_detach, dev, EVHDEV_DETACH_COMPLETE);
}
devremoved(dev);
if (!device_is_quiet(dev))
device_printf(dev, "detached\n");

11
sys/sys/eventhandler.h
View File

@ -293,4 +293,15 @@ typedef void (*swapoff_fn)(void *, struct swdevt *);
EVENTHANDLER_DECLARE(swapon, swapon_fn);
EVENTHANDLER_DECLARE(swapoff, swapoff_fn);
/* newbus device events */
enum evhdev_detach {
EVHDEV_DETACH_BEGIN, /* Before detach() is called */
EVHDEV_DETACH_COMPLETE, /* After detach() returns 0 */
EVHDEV_DETACH_FAILED /* After detach() returns err */
};
typedef void (*device_attach_fn)(void *, device_t);
typedef void (*device_detach_fn)(void *, device_t, enum evhdev_detach);
EVENTHANDLER_DECLARE(device_attach, device_attach_fn);
EVENTHANDLER_DECLARE(device_detach, device_detach_fn);
#endif /* _SYS_EVENTHANDLER_H_ */