Date: Sun, 10 Aug 2003 17:10:30 -0700 From: Marcel Moolenaar <marcel@xcllnt.net> To: threads@FreeBSD.org Subject: KSE/ia64: NULL thread pointer in _thr_sig_add() Message-ID: <20030811001030.GA27859@dhcp42.pn.xcllnt.net>
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Gang,
There seems to be a bug in libkse where we dereference the thread
pointer in situations where it's NULL. I suspect this bug is
specific to platforms that have per-thread thread pointers. I
have some rough gdb(1) support to help out with the analysis:
itanium% /nfs/gnu/obj/gdb/gdb kse kse.core
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This GDB was configured as "ia64-unknown-freebsd5.1"...
Core was generated by `kse'.
Program terminated with signal 4, Illegal instruction.
#0 _thr_sig_add (pthread=0x600000000010e000, sig=11, info=0x6000000000112a40)
at /nfs/freebsd/5.x/src/lib/libpthread/arch/ia64/include/pthread_md.h:189
189 return (_tcb->tcb_thread);
(gdb) l
184 }
185
186 static __inline struct pthread *
187 _get_curthread(void)
188 {
189 return (_tcb->tcb_thread);
190 }
191
192 /*
193 * Get the current kse.
(gdb) bt
#0 _thr_sig_add (pthread=0x6000000000172000, sig=11, info=0x6000000000176a40)
at /nfs/freebsd/5.x/src/lib/libpthread/arch/ia64/include/pthread_md.h:189
#1 0x40000000000099e0 in kse_check_completed (kse=0x600000000001a000)
at /nfs/freebsd/5.x/src/lib/libpthread/thread/thr_kern.c:1556
#2 0x40000000000063c0 in kse_sched_multi (kmbx=0x600000000001a000)
at /nfs/freebsd/5.x/src/lib/libpthread/thread/thr_kern.c:1001
#3 0x0000000000000000 in ?? ()
The illegal instruction fault is caused by a NULL thread pointer:
Dump of assembler code for function _thr_sig_add:
0x400000000001eac0 <_thr_sig_add>: [MII] alloc r40=ar.pfs,13,10,0
0x400000000001eac1 <_thr_sig_add+1>: adds r12=-80,r12
0x400000000001eac2 <_thr_sig_add+2>: mov r41=r1
0x400000000001ead0 <_thr_sig_add+16>: [MII] nop.m 0x0
0x400000000001ead1 <_thr_sig_add+17>: mov r39=b0
0x400000000001ead2 <_thr_sig_add+18>: mov r38=r0
0x400000000001eae0 <_thr_sig_add+32>: [MMI] adds r14=-32,r13;;
0x400000000001eae1 <_thr_sig_add+33>: ld8 r16=[r14]
The fault is given on the last instruction if the disassembly
given above (the thread pointer is r13):
(gdb) info register r13
r13 0x0 0
(gdb) info register r14
r14 0xffffffffffffffe0 -32
Q: Shouldn't we call _tcb_set() somewhere in the code stream to make
sure we have a valid thread pointer?
--
Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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