K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2008-03-17T13:17:10.000000Z
K 7
svn:log
V 1120
Fix two races in the handling of the d_gianttrick for the D_NEEDGIANT
drivers.

In the giant_XXX wrappers for the device methods of the D_NEEDGIANT
drivers, do not dereference the cdev->si_devsw. It is racing with
the destroy_devl() clearing of the si_devsw. Instead, use the
dev_refthread() and return ENXIO for the destroyed device. [1]

The check for the D_INIT in the prep_cdevsw() was not synchronized with
the call of the fini_cdevsw() in destroy_devl(), that under rapid device
creation/destruction may result in the use of uninitialized cdevsw [2].
Change the protocol for the prep_cdevsw(), requiring it to be called
under dev_mtx, where the check for D_INIT is done.

Do not free the memory allocated for the gianttrick cdevsw while holding
the dev_mtx, put it into the free list to be freed later. Reuse the
d_gianttrick pointer to keep the size and layout of the struct cdevsw
(requested by phk). Free the memory in the dev_unlock_and_free(), and do
all the free after the dev_mtx is dropped (suggested by jhb).

Reported by:	bsdimp + many [1], pho [2]
Reviewed by:	phk, jhb
Tested by:	pho
MFC after:	1 week

END