Re: [BUG] perf: can not resolve symbols for forked threads
On Tue, Jun 24, 2014 at 06:47:38AM +, Tony Lu wrote: > >That pthread_exit() is the problem; this results in: > > > >29456 pts/23 Zl 0:00 | \_ [hello] > > > >You want to wait for the threads to complete using pthread_join(). > > > >I suspect the defunct state hides the process. > > Yes, using pthread_join() can workaround this problem. > Does that mean the parent thread can not exit before the child threads? It > still seems like a perf bug. So we scan /proc at record start to acquire the state for the existing tasks, it might be defunct tasks simply aren't there anymore, in which case there's nothing we can do. But I haven't checked.. That said, yes it would be nice if we could cure this. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: [BUG] perf: can not resolve symbols for forked threads
Thanks for your reply.
>-Original Message-
>From: Peter Zijlstra [mailto:pet...@infradead.org]
>Sent: Monday, June 23, 2014 5:13 PM
>To: Tony Lu
>Cc: Paul Mackerras; Ingo Molnar; Arnaldo Carvalho de Melo;
>linux-kernel@vger.kernel.org; Chris Metcalf
>Subject: Re: [BUG] perf: can not resolve symbols for forked threads
>
>On Thu, Jun 19, 2014 at 07:39:42AM +, Tony Lu wrote:
>> Hi
>>
>> I got the below output that shows perf can not resolve symbols for
>> forked threads. I did a system-wide collection from all CPUs after the
>> application hello run.
>
>There's no fork() in... :-)
Yes, but perf regards pthread_created threads as forked threads, and a
PERF_RECORD_FORK event will be delivered when a thread is forked or cloned.
>
>> #include
>> #include
>> #include
>> #include
>> #define NUM_THREADS 5
>>
>> void foo(void)
>> {
>> long i = 10;
>> while (i--) {
>> ;
>> }
>> }
>>
>> void *PrintHello(void *threadid)
>> {
>>long tid;
>>tid = (long)threadid;
>>printf("Hello World! It's me, thread #%ld!\n", tid);
>>foo();
>>pthread_exit(NULL);
>> }
>>
>> int main(int argc, char *argv[])
>> {
>>pthread_t threads[NUM_THREADS];
>>int rc;
>>long t;
>>for(t=0;t> printf("In main: creating thread %ld\n", t);
>> rc = pthread_create(&threads[t], NULL, PrintHello, (void *)t);
>> if (rc){
>>printf("ERROR; return code from pthread_create() is %d\n", rc);
>>exit(-1);
>>}
>> }
>>
>>/* Last thing that main() should do */
>>pthread_exit(NULL);
>> }
>
>That pthread_exit() is the problem; this results in:
>
>29456 pts/23 Zl 0:00 | \_ [hello]
>
>You want to wait for the threads to complete using pthread_join().
>
>I suspect the defunct state hides the process.
Yes, using pthread_join() can workaround this problem.
Does that mean the parent thread can not exit before the child threads? It
still seems like a perf bug.
-Thanks
-Tony
--
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Re: [BUG] perf: can not resolve symbols for forked threads
On Thu, Jun 19, 2014 at 07:39:42AM +, Tony Lu wrote:
> Hi
>
> I got the below output that shows perf can not resolve symbols for
> forked threads. I did a system-wide collection from all CPUs after the
> application hello run.
There's no fork() in... :-)
> #include
> #include
> #include
> #include
> #define NUM_THREADS 5
>
> void foo(void)
> {
> long i = 10;
> while (i--) {
> ;
> }
> }
>
> void *PrintHello(void *threadid)
> {
>long tid;
>tid = (long)threadid;
>printf("Hello World! It's me, thread #%ld!\n", tid);
>foo();
>pthread_exit(NULL);
> }
>
> int main(int argc, char *argv[])
> {
>pthread_t threads[NUM_THREADS];
>int rc;
>long t;
>for(t=0;t printf("In main: creating thread %ld\n", t);
> rc = pthread_create(&threads[t], NULL, PrintHello, (void *)t);
> if (rc){
>printf("ERROR; return code from pthread_create() is %d\n", rc);
>exit(-1);
>}
> }
>
>/* Last thing that main() should do */
>pthread_exit(NULL);
> }
That pthread_exit() is the problem; this results in:
29456 pts/23 Zl 0:00 | \_ [hello]
You want to wait for the threads to complete using pthread_join().
I suspect the defunct state hides the process.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[BUG] perf: can not resolve symbols for forked threads
Hi
I got the below output that shows perf can not resolve symbols for forked
threads. I did a system-wide collection from all CPUs after the application
hello run.
-bash-4.1$ ./perf --version
perf version 3.16.rc1.ge99cfa2
-bash-4.1$ ./hello & ./perf record -a sleep 5
-bash-4.1$ ./perf report
# Overhead Command Shared Object Symbol
# ... .. .
#
54.77%hello [unknown] [.] 0x00400610
28.59%hello [unknown] [.] 0x00400615
16.53%hello [unknown] [.] 0x0040061f
0.01%hello [kernel.kallsyms] [k] __rcu_process_callbacks
0.01% perf [kernel.kallsyms] [k] copy_user_generic_string
0.01%sleep [kernel.kallsyms] [k] filemap_fault
/*
FILE: hello.c
** DESCRIPTION:
** A "hello world" Pthreads program to trigger this bug.
***/
#include
#include
#include
#include
#define NUM_THREADS 5
void foo(void)
{
long i = 10;
while (i--) {
;
}
}
void *PrintHello(void *threadid)
{
long tid;
tid = (long)threadid;
printf("Hello World! It's me, thread #%ld!\n", tid);
foo();
pthread_exit(NULL);
}
int main(int argc, char *argv[])
{
pthread_t threads[NUM_THREADS];
int rc;
long t;
for(t=0;thttp://vger.kernel.org/majordomo-info.html
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