more robust handling of removable devices in GEOM.

This commit (hopefully) improves the situation when a media is removed
quickly after it appeared.  (A number of people have reported this with
USB devices).

There are still a couple of minor races.

Poul-Henning

In message <200304022110.h32LA4WX029838_at_repoman.freebsd.org>, Poul-Henning Kamp
 writes:
>phk         2003/04/02 13:10:04 PST
>
>  FreeBSD src repository
>
>  Modified files:
>    sys/geom             geom.h geom_bsd.c geom_disk.c geom_dump.c 
>                         geom_event.c geom_int.h geom_mbr.c 
>                         geom_pc98.c 
>  Log:
>  Add handling for cancelled events in the g_call_me() methods.
>  
>  Revision  Changes    Path
>  1.53      +2 -0      src/sys/geom/geom.h
>  1.44      +8 -4      src/sys/geom/geom_bsd.c
>  1.65      +15 -2     src/sys/geom/geom_disk.c
>  1.24      +6 -3      src/sys/geom/geom_dump.c
>  1.26      +2 -0      src/sys/geom/geom_event.c
>  1.19      +0 -1      src/sys/geom/geom_int.h
>  1.36      +5 -2      src/sys/geom/geom_mbr.c
>  1.29      +5 -2      src/sys/geom/geom_pc98.c
>

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk_at_FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.