On 01/17/2014 03:52 PM, Arun Chandran wrote:
Hi,
I am testing kgdb on freescale p2020 target.
In target
------------
1)
root@freescale-p2020ds:~# uname -a
Linux freescale-p2020ds 3.10.20-rt14+ #9 SMP Thu Jan 16 16:32:15 IST 2014
ppc GNU/Linux
2)
root@freescale-p2020ds:~# cat /proc/cpuinfo
processor : 0
cpu : e500v2
clock : 999.990008MHz
revision : 4.0 (pvr 8021 1040)
bogomips : 124.99
processor : 1
cpu : e500v2
clock : 999.990008MHz
revision : 4.0 (pvr 8021 1040)
bogomips : 124.99
total bogomips : 249.99
timebase : 62499376
platform : P2020 DS
model : fsl,P2020DS
Memory : 768 MB
3)
freescale-p2020ds:~# echo "ttyS1,115200" >
/sys/module/kgdboc/parameters/kgdoc
4) I set up host (settings given below); Then I send "SysRq : DEBUG"
In host
----------
(gdb) target remote /dev/ttyS0
Remote debugging using /dev/ttyS0
kgdb_breakpoint () at kernel/debug/debug_core.c:1013
1013 arch_kgdb_breakpoint();
(gdb) b sys_sync
Breakpoint 1 at 0xc0167288: file fs/sync.c, line 103.
(gdb) c
Continuing.
I am able to take control in host; after that I am setting breakpoint at
"sys_sync"
In target
------------
root@freescale-p2020ds:~# for i in 1 2 3 4 5 6 7 8 9
do
sync
done
In host
----------
Breakpoint 1, sys_sync () at fs/sync.c:103
103 {
(gdb) c
Continuing.
Breakpoint is hit only one time instead of 9 times; after that target hangs.
I recommend you try upstream to take a further look at this, instead of that
Freescale distribution. As I recall currently KGDB works well in 85xx case in ML.
Then i tried to send "SysRq : DEBUG" in target kernel panics.
I have pasted the panic below.
#########################################
SysRq : DEBUG
Kernel panic - not syncing: Recursive entry to debugger
The kernel already trap into kgdb_handle_exception() with the debug exception
while triggering that break point, but again you trigger another debug exception
by SysRq. Actually KGDB can't handle such this recursive behavior, so KGDB
always call kgdb_reenter_check() to prevent this scenario with this call trace.
static int kgdb_reenter_check(struct kgdb_state *ks)
{
unsigned long addr;
if (atomic_read(&kgdb_active) != raw_smp_processor_id())
return 0;
...
if (exception_level > 1) {
dump_stack();
panic("Recursive entry to debugger");
}
Tiejun
CPU: 1 PID: 2266 Comm: cron Not tainted 3.10.20-rt14+ #6
Call Trace:
[effe5d10] [c0008060] show_stack+0x4c/0x168 (unreliable)
[effe5d50] [c0588878] panic+0xe4/0x224
[effe5da0] [c00b2cbc] kgdb_handle_exception+0x1d4/0x1f8
[effe5df0] [c0010038] kgdb_handle_breakpoint+0x4c/0x80
[effe5e00] [c057e7e0] program_check_exception+0x10c/0x264
[effe5e10] [c000f660] ret_from_except_full+0x0/0x4c
--- Exception: 700 at sysrq_handle_dbg+0x3c/0xc8
LR = __handle_sysrq+0x154/0x1cc
[effe5ed0] [c033df5c] __handle_sysrq+0x140/0x1cc (unreliable)
[effe5f00] [c0353ef8] serial8250_rx_chars+0xe8/0x218
[effe5f30] [c0359644] fsl8250_handle_irq+0xac/0x174
[effe5f50] [c0352f9c] serial8250_interrupt+0x40/0xe8
[effe5f70] [c00b5500] handle_irq_event_percpu+0xcc/0x2a8
[effe5fc0] [c00b5720] handle_irq_event+0x44/0x74
[effe5fe0] [c00b8e14] handle_fasteoi_irq+0xd0/0x17c
[effe5ff0] [c000d58c] call_handle_irq+0x18/0x28
[c4f91b10] [c0004f60] do_IRQ+0x150/0x224
[c4f91b40] [c000f6ac] ret_from_except+0x0/0x18
--- Exception: 501 at rpcauth_lookup_credcache+0x138/0x2a4
LR = rpcauth_lookup_credcache+0xb8/0x2a4
[c4f91c00] [24002424] 0x24002424 (unreliable)
[c4f91c50] [c055cb84] rpcauth_lookupcred+0x64/0xac
[c4f91c80] [c055ce2c] rpcauth_refreshcred+0x11c/0x124
[c4f91cc0] [c055ac80] __rpc_execute+0x8c/0x330
[c4f91d10] [c05540b8] rpc_run_task+0x9c/0xc4
[c4f91d20] [c0554204] rpc_call_sync+0x50/0xb8
[c4f91d50] [c0257164] nfs_proc_getattr+0x48/0x5c
[c4f91d70] [c024aaa4] __nfs_revalidate_inode+0xa8/0x168
[c4f91d90] [c024ac1c] nfs_revalidate_mapping+0xb8/0x194
[c4f91da0] [c0251f00] nfs_follow_link+0x24/0xc8
[c4f91dc0] [c0145280] path_lookupat+0x2f4/0x824
[c4f91e10] [c01457dc] filename_lookup.isra.33+0x2c/0x8c
[c4f91e30] [c0147a74] user_path_at_empty+0x58/0x9c
[c4f91eb0] [c013d5bc] vfs_fstatat+0x54/0xb4
[c4f91ee0] [c013d93c] SyS_stat64+0x1c/0x44
[c4f91f40] [c000eec0] ret_from_syscall+0x0/0x3c
--- Exception: c01 at 0xff08a98
LR = 0xfed53e8
CPU: 1 PID: 2266 Comm: cron Not tainted 3.10.20-rt14+ #6
Call Trace:
[effe5bb0] [c0008060] show_stack+0x4c/0x168 (unreliable)
[effe5bf0] [c00b2cac] kgdb_handle_exception+0x1c4/0x1f8
[effe5c40] [c0010038] kgdb_handle_breakpoint+0x4c/0x80
[effe5c50] [c057e7e0] program_check_exception+0x10c/0x264
[effe5c60] [c000f660] ret_from_except_full+0x0/0x4c
--- Exception: 700 at kgdb_panic_event+0x1c/0x3c
LR = notifier_call_chain+0x60/0xb0
[effe5d20] [00000000] (nil) (unreliable)
[effe5d40] [c05819dc] __atomic_notifier_call_chain+0x14/0x24
[effe5d50] [c05888a8] panic+0x114/0x224
[effe5da0] [c00b2cbc] kgdb_handle_exception+0x1d4/0x1f8
[effe5df0] [c0010038] kgdb_handle_breakpoint+0x4c/0x80
[effe5e00] [c057e7e0] program_check_exception+0x10c/0x264
[effe5e10] [c000f660] ret_from_except_full+0x0/0x4c
--- Exception: 700 at sysrq_handle_dbg+0x3c/0xc8
LR = __handle_sysrq+0x154/0x1cc
[effe5ed0] [c033df5c] __handle_sysrq+0x140/0x1cc (unreliable)
[effe5f00] [c0353ef8] serial8250_rx_chars+0xe8/0x218
[effe5f30] [c0359644] fsl8250_handle_irq+0xac/0x174
[effe5f50] [c0352f9c] serial8250_interrupt+0x40/0xe8
[effe5f70] [c00b5500] handle_irq_event_percpu+0xcc/0x2a8
[effe5fc0] [c00b5720] handle_irq_event+0x44/0x74
[effe5fe0] [c00b8e14] handle_fasteoi_irq+0xd0/0x17c
[effe5ff0] [c000d58c] call_handle_irq+0x18/0x28
[c4f91b10] [c0004f60] do_IRQ+0x150/0x224
[c4f91b40] [c000f6ac] ret_from_except+0x0/0x18
--- Exception: 501 at rpcauth_lookup_credcache+0x138/0x2a4
LR = rpcauth_lookup_credcache+0xb8/0x2a4
[c4f91c00] [24002424] 0x24002424 (unreliable)
[c4f91c50] [c055cb84] rpcauth_lookupcred+0x64/0xac
[c4f91c80] [c055ce2c] rpcauth_refreshcred+0x11c/0x124
[c4f91cc0] [c055ac80] __rpc_execute+0x8c/0x330
[c4f91d10] [c05540b8] rpc_run_task+0x9c/0xc4
[c4f91d20] [c0554204] rpc_call_sync+0x50/0xb8
[c4f91d50] [c0257164] nfs_proc_getattr+0x48/0x5c
[c4f91d70] [c024aaa4] __nfs_revalidate_inode+0xa8/0x168
[c4f91d90] [c024ac1c] nfs_revalidate_mapping+0xb8/0x194
[c4f91da0] [c0251f00] nfs_follow_link+0x24/0xc8
[c4f91dc0] [c0145280] path_lookupat+0x2f4/0x824
[c4f91e10] [c01457dc] filename_lookup.isra.33+0x2c/0x8c
[c4f91e30] [c0147a74] user_path_at_empty+0x58/0x9c
[c4f91eb0] [c013d5bc] vfs_fstatat+0x54/0xb4
[c4f91ee0] [c013d93c] SyS_stat64+0x1c/0x44
[c4f91f40] [c000eec0] ret_from_syscall+0x0/0x3c
--- Exception: c01 at 0xff08a98
LR = 0xfed53e8
########################################################
Could you please share your thoughts on this issue?
I have also attached my kernel .config.
Regards,
Arun C
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