panic: Lock GEOM topology not exclusively locked

[Peter Holm]

With GENERIC HEAD from May 5 04:56 UTC I got:

panic(c0841f8c,c083c2d3,c083c608,1d8,1) at panic+0x14b
_sx_assert(c0906ae0,4,c083c608,1d8) at _sx_assert+0x77
g_new_providerf(c1733900,c081aeee,0,1,c168b804) at g_new_providerf+0x1f
acd_read_toc(c16af780,0,c091c1a0,0,0) at acd_read_toc+0x1c0
acd_geom_ioctl(c1733880,c00c6303,c16ba7b0,5,c1863600) at acd_geom_ioctl+0x6a
g_dev_ioctl(c174d500,c00c6303,c16ba7b0,5,c1863600) at g_dev_ioctl+0x1cf
devfs_ioctl_f(c181a360,c00c6303,c16ba7b0,c19f7780,c1863600) at devfs_ioctl_f+0xc7
ioctl(c1863600,cf387d04,3,45,200246) at ioctl+0x370
syscall(80c003b,80c003b,bfbf003b,bfbfd8fc,80fc100) at syscall+0x227

Details at http://www.holm.cc/stress/log/cons128.html
-- 
Peter Holm