QemuKernelDebug
Javier Cardona edited this page Mar 6, 2012
·
2 revisions
In your .config
CONFIG_DEBUG_INFO=y
qemu -kernel (...) -gdb tcp::1234
gdb /path/to/vmlinux
in gdb
target remote localhost:1234
#0 ?? () at arch/x86/lib/semaphore_32.S:59
#1 0xc14aa9b2 in arch_read_lock (lock=0xc16fb460) at /home/javier/dev/wireless-testing/arch/x86/include/asm/spinlock.h:251
#2 __raw_read_lock (lock=0xc16fb460) at include/linux/rwlock_api_smp.h:150
#3 _raw_read_lock (lock=0xc16fb460) at kernel/spinlock.c:209
#4 0xc14848b1 in mesh_path_add (dst=, sdata=0xc6d56400) at net/mac80211/mesh_pathtbl.c:283
#5 0xc148645e in hwmp_route_info_get (sdata=0xc6d56400, mgmt=, hwmp_ie=, action=MPATH_PREQ) at net/mac80211/mesh_hwmp.c:401
#6 0xc14865e0 in mesh_rx_path_sel_frame (sdata=0xc6d56400, mgmt=, len=) at net/mac80211/mesh_hwmp.c:744
#7 0xc1483c02 in ieee80211_mesh_rx_mgmt_action (sdata=0xc16fb460, skb=) at net/mac80211/mesh.c:607
#8 ieee80211_mesh_rx_queued_mgmt (sdata=0xc16fb460, skb=) at net/mac80211/mesh.c:633
#9 0xc1474881 in ieee80211_iface_work (work=) at net/mac80211/iface.c:807
#10 0xc1040d0b in process_one_work (worker=0xc6e01480, work=0xc6d56694) at kernel/workqueue.c:1862
#11 0xc1042143 in worker_thread (__worker=) at kernel/workqueue.c:1973
#12 0xc1044f0d in kthread (_create=0xc7563f18) at kernel/kthread.c:96
#13 0xc14b0036 in ?? () at arch/x86/kernel/entry_32.S:1011
#14 0x00000000 in ?? ()
For the bug above apparently we could have obtained the same result without gdb by enabling CONFIG_LOCKUP_DETECTOR=y in your kernel. This would dump a stack trace after looping more than 10 seconds if kernel mode.
Indeed:
[ 293.386049] [] do_raw_read_lock+0x26/0x29
[ 293.386049] [] _raw_read_lock+0x8/0xa
[ 293.386049] [] mesh_path_add+0xb7/0x24e
[ 293.386049] [] ? mesh_path_lookup+0x1b/0xa6
[ 293.386049] [] hwmp_route_info_get+0x276/0x2fd
[ 293.386049] [] mesh_rx_path_sel_frame+0x5a/0x5d9
[ 293.386049] [] ? update_curr+0x1cf/0x1d7
[ 293.386049] [] ieee80211_mesh_rx_queued_mgmt+0x60/0x67
[ 293.386049] [] ieee80211_iface_work+0x1f0/0x258
[ 293.386049] [] process_one_work+0x192/0x269
[ 293.386049] [] ? ieee80211_teardown_sdata+0xaf/0xaf
[ 293.386049] [] worker_thread+0xf7/0x1fe
[ 293.386049] [] ? complete+0x34/0x3e
[ 293.386049] [] ? manage_workers+0x164/0x164
[ 293.386049] [] kthread+0x62/0x67
[ 293.386049] [] ? __init_kthread_worker+0x28/0x28
[ 293.386049] [] kernel_thread_helper+0x6/0xd