Hi all,
The kernel I've made with 'mtx_assert(&Giant, MA_OWNED);' in all tty functions
works fine. I'm not able to crash it yet, even under 24 hour load.
But I have also seen what appears to be strange interactions or races between
devfs and the TTY code before the Giant push down here, which was causing me
some problems. After some discussions with John and Bruce, it looks like the
manipulation of t_session should be protected by Giant.
I Agree. This backout doesn't solve this panic here. I got this panic on FreeBSD
5.3 RELEASE and 5.4 RELEASE too. Exactly the same trace. And revision 1.272
never made it into RELENG_5.
#1 0xc066355e in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:409
#2 0xc06638b5 in panic (fmt=0xc0891732 "%s") at
/usr/src/sys/kern/kern_shutdown.c:565
#3 0xc085c6b6 in trap_fatal (frame=0xed6e4ab8, eva=4) at
/usr/src/sys/i386/i386/trap.c:836
#4 0xc085c3bf in trap_pfault (frame=0xed6e4ab8, usermode=0, eva=4) at
/usr/src/sys/i386/i386/trap.c:744
#5 0xc085bfb5 in trap (frame=
{tf_fs = 8, tf_es = 40, tf_ds = -1063714776, tf_edi = -1064042304, tf_esi
= 0, tf_ebp = -311538944, tf_isp = -311538972, tf_ebx
= -967615488, tf_edx = -1063651212, tf_ecx = -941099136, tf_eax = 0, tf_trapno =
12, tf_err = 0, tf_eip = -1066845359, tf_cs = 32,
tf_eflags = 66194, tf_esp = -967615488, tf_ss = 0})
at /usr/src/sys/i386/i386/trap.c:434
#6 0xc0848bea in calltrap () at /usr/src/sys/i386/i386/exception.s:139
#7 0xc0693b51 in ttymodem (tp=0xc6535c00, flag=-1063651212) at
/usr/src/sys/kern/tty.c:1659
#8 0xc0698362 in ptcclose (dev=0x0, flags=3, fmt=8192, td=0xc7e7f780) at
linedisc.h:136
#9 0xc0638a6f in giant_close (dev=0xcb3c1100, fflag=3, devtype=8192,
td=0xc7e7f780) at /usr/src/sys/kern/kern_conf.c:266
#10 0xc06162bf in devfs_close (ap=0xed6e4b7c) at
/usr/src/sys/fs/devfs/devfs_vnops.c:287
#11 0xc086dc1c in VOP_CLOSE_APV (vop=0x0, a=0xc099f874) at vnode_if.c:426
#12 0xc06c87e2 in vn_close (vp=0xc9cdf660, flags=3, file_cred=0x0,
td=0xc7e7f780) at vnode_if.h:227
#13 0xc06c974a in vn_closefile (fp=0xc6fc5438, td=0xc7e7f780) at
/usr/src/sys/kern/vfs_vnops.c:865
#14 0xc06162e7 in devfs_close_f (fp=0xc6fc5438, td=0xc7e7f780) at
/usr/src/sys/fs/devfs/devfs_vnops.c:297
#15 0xc0642cdc in fdrop_locked (fp=0xc6fc5438, td=0xc7e7f780) at file.h:295
#16 0xc0642c29 in fdrop (fp=0xc6fc5438, td=0xc7e7f780) at
/usr/src/sys/kern/kern_descrip.c:2122
#17 0xc06411c7 in closef (fp=0xc6fc5438, td=0xc7e7f780) at
/usr/src/sys/kern/kern_descrip.c:1942
#18 0xc063e329 in close (td=0xc7e7f780, uap=0x0) at
/usr/src/sys/kern/kern_descrip.c:1007
Back out one of the Giant removals from revision 1.272. Giant was not here to
protect the vnode, it was present to synchronize access to TTY session
information between exit(2) and the TTY code. While we are here, note that
Giant is required for TTY protection.
Clue from: bde
Discussed with: jhb
MFC after: 1 week
Revision Changes Path
1.290 +2 -2 src/sys/kern/kern_exit.c
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