Date: Mon, 27 Aug 2001 13:43:41 +0400 (MSD) From: "Eugene L. Vorokov" <vel@bugz.infotecs.ru> To: freebsd-hackers@freebsd.org Subject: problem with unloading device driver Message-ID: <200108270943.f7R9hf901857@bugz.infotecs.ru>
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Hello,
I have a module which adds new device. It does make_dev() and then simulates
mknod() syscall, so that /dev/name is always automatically created.
Also I have a daemon which reads from and writes to this device. The daemon
opens the device once and then holds it open. When my module unloads,
it simulates unlink() and then does detsroy_dev(). I just noticed that
when I unload my module, the first write() by daemon to the fd associated with
that device causes system to crash. Trace looks like this:
(kgdb) bt
#0 dumpsys () at /usr/src/sys/kern/kern_shutdown.c:487
#1 0xc0177ed7 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:330
#2 0xc01782f1 in panic (fmt=0xc0276af8 "bwrite: buffer is not busy???") at /usr/src/sys/kern/kern_shutdown.c:623
#3 0xc01a4a7b in bwrite (bp=0xc26b2390) at /usr/src/sys/kern/vfs_bio.c:672
#4 0xc01a5d08 in vfs_bio_awrite (bp=0xc26b2390) at /usr/src/sys/kern/vfs_bio.c:1538
#5 0xc01580ac in spec_fsync (ap=0xc7319cec) at /usr/src/sys/fs/specfs/spec_vnops.c:400
#6 0xc0157cb9 in spec_vnoperate (ap=0xc7319cec) at /usr/src/sys/fs/specfs/spec_vnops.c:119
#7 0xc02161bc in ffs_sync (mp=0xc05ac000, waitfor=2, cred=0xc05b1d00, p=0xc02d3fa0) at vnode_if.h:441
#8 0xc01b1677 in sync (p=0xc02d3fa0, uap=0x0) at /usr/src/sys/kern/vfs_syscalls.c:622
#9 0xc0177acb in boot (howto=256) at /usr/src/sys/kern/kern_shutdown.c:239
#10 0xc01782f1 in panic (fmt=0xc0288ffe "%s") at /usr/src/sys/kern/kern_shutdown.c:623
#11 0xc025337b in trap_fatal (frame=0xc7319dec, eva=12) at /usr/src/sys/i386/i386/trap.c:936
#12 0xc02530c5 in trap_pfault (frame=0xc7319dec, usermode=0, eva=12) at /usr/src/sys/i386/i386/trap.c:850
#13 0xc0252a44 in trap (frame={tf_fs = -953090024, tf_es = -953090032, tf_ds = -1071972336, tf_edi = -953049344,
tf_esi = -952992672, tf_ebp = -953049500, tf_isp = -953049576, tf_ebx = -1053283072, tf_edx = -953049456, tf_ecx = 7,
tf_eax = 0, tf_trapno = 12, tf_err = 0, tf_eip = -1072332928, tf_cs = 8, tf_eflags = 66195, tf_esp = -1053283072,
tf_ss = -953049344}) at /usr/src/sys/i386/i386/trap.c:405
#14 0xc0157f80 in spec_write (ap=0xc7319e90) at /usr/src/sys/fs/specfs/spec_vnops.c:289
#15 0xc0157cb9 in spec_vnoperate (ap=0xc7319e90) at /usr/src/sys/fs/specfs/spec_vnops.c:119
#16 0xc01b6f6b in vn_write (fp=0xc137f280, uio=0xc7319f00, cred=0xc1363800, flags=0, p=0xc72a5540) at vnode_if.h:303
#17 0xc018fc18 in dofilewrite (p=0xc72a5540, fp=0xc137f280, fd=3, buf=0xbfbffbab, nbyte=1, offset=-1, flags=0)
at /usr/src/sys/sys/file.h:162
#18 0xc018face in write (p=0xc72a5540, uap=0xc7319f80) at /usr/src/sys/kern/sys_generic.c:334
#19 0xc02538a5 in syscall (frame={tf_fs = 47, tf_es = 47, tf_ds = 47, tf_edi = -1077937128, tf_esi = -1077937136,
tf_ebp = -1077937220, tf_isp = -953049132, tf_ebx = 1, tf_edx = 0, tf_ecx = 0, tf_eax = 4, tf_trapno = 12, tf_err = 2,
tf_eip = 671760164, tf_cs = 31, tf_eflags = 663, tf_esp = -1077937280, tf_ss = 47}) at /usr/src/sys/i386/i386/trap.c:1123
#20 0xc024479d in syscall_with_err_pushed ()
#21 0x80486bd in ?? ()
(kgdb) frame 14
#14 0xc0157f80 in spec_write (ap=0xc7319e90) at /usr/src/sys/fs/specfs/spec_vnops.c:289
289 error = (*devsw(dev)->d_write) (dev, uio, ap->a_ioflag);
(kgdb) p *dev
$2 = {si_flags = 0, si_atime = {tv_sec = 998903778, tv_nsec = 2619315}, si_ctime = {tv_sec = 998903780, tv_nsec = 22640918},
si_mtime = {tv_sec = 998903780, tv_nsec = 22640918}, si_udev = 8448, si_hash = {le_next = 0xc02bcd38, le_prev = 0xc02bdca4},
si_hlist = {slh_first = 0xc7327c60}, si_children = {lh_first = 0x0}, si_siblings = {le_next = 0x0, le_prev = 0x0},
si_parent = 0x0, si_snapshots = {tqh_first = 0x0, tqh_last = 0xc1382d3c}, si_copyonwrite = 0, si_inode = 0,
si_name = "paudit\000\000\000\000\000\000\000\000\000", si_drv1 = 0x0, si_drv2 = 0x0, si_devsw = 0x0, si_iosize_max = 65536,
si_uid = 0, si_gid = 0, si_mode = 438, __si_u = {__si_tty = {__sit_tty = 0x0}, __si_disk = {__sid_disk = 0x0,
__sid_mountpoint = 0x0, __sid_bsize_phys = 0, __sid_bsize_best = 0}}}
si_devsw is 0 here, which seems to be a problem.
Is this a bug, or can I do something inside my module to prevent this
from happening ?
Regards,
Eugene
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