Hi Jam/Anand(?)
Can you reproduce this against lttng 2.7 or master (ust/tools) ?
Thanks
On 2015-08-06 01:11 PM, jamie explorer wrote:
Hi All,
i looked into this further, generated .c file with expanded macros for
debugging
Some of the function pointer are not populated correctly.
as i mentioned this issue is only seen using g++ compiler and not seen
with gcc
please see the following GDB analysis:
(gdb) bt
#0 0x00000000 in ?? ()
#1 0x080490a0 in __event_probe__sample_tracepoint___message
(__tp_data=0x80512d0,
text=0x804ca64 "Hello World\n") at sample_tracepoint.c:8567
#2 0x0804ba23 in __tracepoint_cb_sample_tracepoint___message (
text=0x804ca64 "Hello World\n")
at /build/home/jam/gentp/src/sample.c:4026
#3 main (argc=1, argv=0xffffdd74)
at /build/home/jam/gentp/src/sample.c:4731
****bc_runtime->filter* --- is not populated correctly, because of
which it crashes
*(gdb) frame 1*
#1 0x080490a0 in __event_probe__sample_tracepoint___message
(__tp_data=0x80512d0,
text=0x804ca64 "Hello World\n") at sample_tracepoint.c:8567
8567 if (__builtin_expect(!!(*bc_runtime->filter*(bc_runtime,
__stackvar.__filter_stack_data) & LTTNG_FILTER_RECORD_FLAG), 0))
*(gdb) list*
8562 (__stackvar.__filter_stack_data, __tp_data,text);
8563 for (bc_runtime = ((__typeof__(*bc_runtime) *) ((char *)
((reinterpret_cast<__typeof__((&__event->bytecode_runtime_head)->next)>(tracepoint_dlopen.rcu_dereference_sym_bp((reinterpret_cast<void
*>((&__event->bytecode_runtime_head)->next)))))) - (unsigned long)
(&((__typeof__(*bc_runtime) *) 0)->node)));
8564 &bc_runtime->node != (&__event->bytecode_runtime_head);
8565 bc_runtime = ((__typeof__(*bc_runtime) *) ((char *)
((reinterpret_cast<__typeof__(bc_runtime->node.next)>(tracepoint_dlopen.rcu_dereference_sym_bp((reinterpret_cast<void
*>(bc_runtime->node.next)))))) - (unsigned long)
(&((__typeof__(*bc_runtime) *) 0)->node))))
8566 {
*8567 if (__builtin_expect(!!(bc_runtime->filter(bc_runtime,
__stackvar.__filter_stack_data) & LTTNG_FILTER_RECORD_FLAG), 0))*
8568 __filter_record = 1;
8569 } if (__builtin_expect(!!(!__filter_record), 1)) return;
8570 } __event_len =
8571
*printing bc_runtime shows filter is 0*
*(gdb) p *bc_runtime *
$3 = {bc = 0x0,* filter = 0x0,* link_failed = 0, node = {next =
0x8051304,
prev = 0x8051304}}
*also i see __event->bytecode_runtime_head->prev = 0x1 which may be wrong*
*(gdb) p *__event*
$4 = {id = 2, chan = 0xf6c047c0, enabled = 1,
desc = 0x804c700 <__event_desc___sample_tracepoint_message>,
_deprecated1 = 0x0,
ctx = 0x0, instrumentation = LTTNG_UST_TRACEPOINT, u = {<No data
fields>}, node = {
next = 0x8051344, prev = 0x0}, _deprecated2 = {next = 0x0, prev =
0x0},
_deprecated3 = 0x0, _deprecated4 = 0, *bytecode_runtime_head = {next
= 0x8051304,
prev = 0x1}*, has_enablers_without_bytecode = 134552592,
enablers_ref_head = {
next = 0x8051c10, prev = 0x0}, hlist = {next = 0xf6c00ea0, prev =
0x1},
registered = 89}
I guess this structure is populated in tracepoint_register using urcu.
Can anyone give me more pointers to debug this. Is this a known issue
and is there any patch which i can use
/Jam
On Mon, Aug 3, 2015 at 4:19 PM, jamie explorer
<[email protected] <mailto:[email protected]>> wrote:
Hi,
i am trying to run 32-bit application and see crash at the the
line where "tracepoint" is used.
i am using sample application given in
lttng-ust-2.6.0/doc/examples/gen-tp/
Not able to understand why the problem is seen only with 32-bit
apps? Can experts here pls help me fix this.
Have tried using ELF 32-bit app on Intel 80386 and PowerPC and see
the crash. Where as 64-bit applications have no problem.
following is the code where it crashes
for (i = 0; i < 100000; i++) {
tracepoint(sample_tracepoint, message, "Hello
World\n"); <<<< Crash here
usleep(1);
}
GDB output:
#0 0x00000000 in ?? ()
#1 0x10001e54 in __event_probe__sample_tracepoint___message (
__tp_data=0x10015420, text=0x100034a4 "Hello World\n")
at /build/home/jam/gentp/sample_tracepoint.h:13
#2 0x10000b9c in __tracepoint_cb_sample_tracepoint___message (
text=0x100034a4 "Hello World\n")
at //build/home/jam/gentp/sample_tracepoint.h:13
#3 main (argc=<optimized out>, argv=<optimized out>)
at /build/home/jam/gentp/sample.c:115
i am running 32-bit version of lttng-sessiond
root@host:~# ps aux | grep lttng
root 4224 0.0 0.0 92212 1648 ? Ssl 00:42 0:00
/usr/bin/lttng-sessiond --consumerd32-path
/usr/lib/lttng/libexec/lttng-consumerd --consumerd32-libdir
/usr/lib/ -b --no-kernel
root 4243 0.0 0.0 64212 956 ? Sl 00:42 0:00
lttng-consumerd -u --consumerd-cmd-sock
/var/run/lttng/ustconsumerd32/command --consumerd-err-sock
/var/run/lttng/ustconsumerd32/error --group tracing
/Jam
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Jonathan R. Julien
Efficios
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