[lttng-dev] Tracepoints for pthreads conditional variables
Shehab Elsayed
shehabyomn at gmail.com
Tue May 29 10:36:07 EDT 2018
I was wondering if you had a chance to look over this issue. Thanks!
Shehab Y. Elsayed, MSc.
PhD Student
The Edwards S. Rogers Sr. Dept. of Electrical and Computer Engineering
University of Toronto
E-mail: shehabyomn at gmail.com
<https://webmail.rice.edu/imp/message.php?mailbox=INBOX&index=11#>
On Thu, May 3, 2018 at 4:37 PM, Shehab Elsayed <shehabyomn at gmail.com> wrote:
> Thanks for the reply. Here is a link to the repo https://github.com/
> ShehabElsayed/LTTng_debugging.git
>
> It contains the LTTng source code I am using and one of the benchmarks
> that is causing problems.
>
> Shehab Y. Elsayed, MSc.
> PhD Student
> The Edwards S. Rogers Sr. Dept. of Electrical and Computer Engineering
> University of Toronto
> E-mail: shehabyomn at gmail.com
> <https://webmail.rice.edu/imp/message.php?mailbox=INBOX&index=11#>
>
> On Tue, May 1, 2018 at 10:39 AM, Jonathan Rajotte-Julien <
> jonathan.rajotte-julien at efficios.com> wrote:
>
>> Hi Shehab,
>>
>> Please provide a link to a lttng-ust git tree or an actual patch (git
>> format-patch).
>> This will help any person who might be interested in helping you including
>> myself.
>>
>> Cheers
>>
>> On Tue, May 01, 2018 at 09:31:52AM -0400, Shehab Elsayed wrote:
>> > Hi,
>> >
>> > I am trying to create wrappers for pthreads conditional variables
>> functions
>> > (wait, signal and broadcast) to insert tracepoints. I followed the same
>> > approach done for the mutex functions already provided with lttng,
>> however
>> > I am running into some problems. Mainly the applications seem to get
>> stuck
>> > when the conditional variable wrappers are enabled.
>> >
>> > Here is my implementation for the wrapper functions:
>> > int pthread_cond_wait(pthread_cond_t *condition, pthread_mutex_t
>> > *mutex)
>> >
>> > {
>> >
>> > static int (*cond_wait)(pthread_cond_t *, pthread_mutex_t
>> > *);
>> > int retval;
>> >
>> >
>> >
>> > if (!cond_wait)
>> > {
>> >
>> > cond_wait = dlsym(RTLD_NEXT, "pthread_cond_wait");
>> >
>> > if (!cond_wait)
>> > {
>> >
>> > if (thread_in_trace)
>> > {
>> >
>> >
>> > abort();
>> >
>> >
>> > }
>> >
>> > fprintf(stderr, "unable to initialize pthread wrapper
>> > library.\n");
>> > return EINVAL;
>> >
>> >
>> > }
>> >
>> >
>> > }
>> >
>> > if (thread_in_trace)
>> > {
>> >
>> > return cond_wait(condition, mutex);
>> >
>> >
>> > }
>> >
>> >
>> >
>> > thread_in_trace =
>> > 1;
>> >
>> > tracepoint(lttng_ust_pthread, pthread_cond_wait_begin, condition,
>> > mutex,
>> >
>> > LTTNG_UST_CALLER_IP());
>> >
>> > retval = cond_wait(condition, mutex);
>> >
>> > tracepoint(lttng_ust_pthread, pthread_cond_wait_end, condition,
>> > mutex,
>> >
>> > LTTNG_UST_CALLER_IP());
>> >
>> > thread_in_trace =
>> > 0;
>> >
>> > return retval;
>> >
>> > }
>> >
>> >
>> >
>> > int pthread_cond_signal(pthread_cond_t
>> > *condition)
>> >
>> > {
>> >
>> > static int (*cond_signal)(pthread_cond_t
>> > *);
>> >
>> > int retval;
>> >
>> >
>> >
>> > if (!cond_signal)
>> > {
>> >
>> > cond_signal = dlsym(RTLD_NEXT, "pthread_cond_signal");
>> >
>> > if (!cond_signal)
>> > {
>> >
>> > if (thread_in_trace)
>> > {
>> >
>> >
>> > abort();
>> >
>> >
>> > }
>> >
>> > fprintf(stderr, "unable to initialize pthread wrapper
>> > library.\n");
>> > return EINVAL;
>> >
>> >
>> > }
>> >
>> >
>> > }
>> >
>> > if (thread_in_trace)
>> > {
>> >
>> > return cond_signal(condition);
>> >
>> >
>> > }
>> >
>> >
>> >
>> > thread_in_trace =
>> > 1;
>> >
>> > tracepoint(lttng_ust_pthread, pthread_cond_signal_begin,
>> > condition,
>> > LTTNG_UST_CALLER_IP());
>> >
>> > retval = cond_signal(condition);
>> >
>> > tracepoint(lttng_ust_pthread, pthread_cond_signal_end,
>> > condition,
>> > LTTNG_UST_CALLER_IP());
>> >
>> > thread_in_trace =
>> > 0;
>> >
>> > return retval;
>> >
>> > }
>> >
>> >
>> >
>> > int pthread_cond_broadcast(pthread_cond_t
>> > *condition)
>> >
>> > {
>> >
>> > static int (*cond_broadcast)(pthread_cond_t
>> > *);
>> > int retval;
>> >
>> >
>> >
>> > if (!cond_broadcast)
>> > {
>> >
>> > cond_broadcast = dlsym(RTLD_NEXT, "pthread_cond_broadcast");
>> >
>> > if (!cond_broadcast)
>> > {
>> >
>> > if (thread_in_trace)
>> > {
>> >
>> >
>> > abort();
>> >
>> >
>> > }
>> >
>> > fprintf(stderr, "unable to initialize pthread wrapper
>> > library.\n");
>> > return EINVAL;
>> >
>> >
>> > }
>> >
>> >
>> > }
>> >
>> > if (thread_in_trace)
>> > {
>> >
>> > return cond_broadcast(condition);
>> >
>> >
>> > }
>> >
>> >
>> >
>> > thread_in_trace =
>> > 1;
>> >
>> > tracepoint(lttng_ust_pthread, pthread_cond_broadcast_begin,
>> > condition,
>> > LTTNG_UST_CALLER_IP());
>> >
>> > retval = cond_broadcast(condition);
>> >
>> > tracepoint(lttng_ust_pthread, pthread_cond_broadcast_end,
>> > condition,
>> > LTTNG_UST_CALLER_IP());
>> >
>> > thread_in_trace =
>> > 0;
>> >
>> > return retval;
>> >
>> > }
>> >
>> > Things I have tried:
>> > 1- Comment out pthread_cond_wait function --> segmentation fault
>> > 2- Comment out pthread_cond_signal and _broadcast --> stuck (I can see
>> the
>> > program is still running but nor forward progress is being made)
>> compared
>> > to the case when the wrappers are not preloaded.
>> > 3- Comment out all tracepoint related code (basically the wrapper just
>> call
>> > the corresponding pthreads function) --> same results as points 1 and 2.
>> >
>> > Any idea what might be causing this or how I could debug this problem?
>> >
>> > Thank you very much in advance.
>> >
>> > Best Regards,
>> > Shehab
>>
>> > int pthread_cond_wait(pthread_cond_t *condition, pthread_mutex_t
>> *mutex)
>> > {
>>
>>
>>
>> > static int (*cond_wait)(pthread_cond_t *, pthread_mutex_t *);
>>
>> > int retval;
>>
>> >
>>
>> > if (!cond_wait) {
>>
>> > cond_wait = dlsym(RTLD_NEXT, "pthread_cond_wait");
>>
>> > if (!cond_wait) {
>>
>> > if (thread_in_trace) {
>>
>> > abort();
>>
>> > }
>>
>> > fprintf(stderr, "unable to initialize pthread wrapper
>> library.\n");
>> > return EINVAL;
>>
>> > }
>>
>> > }
>>
>> > if (thread_in_trace) {
>>
>> > return cond_wait(condition, mutex);
>>
>> > }
>>
>> >
>>
>> > thread_in_trace = 1;
>>
>> > tracepoint(lttng_ust_pthread, pthread_cond_wait_begin, condition,
>> mutex,
>> > LTTNG_UST_CALLER_IP());
>>
>> > retval = cond_wait(condition, mutex);
>>
>> > tracepoint(lttng_ust_pthread, pthread_cond_wait_end, condition,
>> mutex,
>> > LTTNG_UST_CALLER_IP());
>>
>> > thread_in_trace = 0;
>>
>> > return retval;
>>
>> > }
>>
>> >
>>
>> > int pthread_cond_signal(pthread_cond_t *condition)
>>
>> > {
>>
>> > static int (*cond_signal)(pthread_cond_t *);
>>
>> > int retval;
>>
>> >
>>
>> > if (!cond_signal) {
>>
>> > cond_signal = dlsym(RTLD_NEXT, "pthread_cond_signal");
>>
>> > if (!cond_signal) {
>>
>> > if (thread_in_trace) {
>>
>> > abort();
>>
>> > }
>>
>> > fprintf(stderr, "unable to initialize pthread wrapper
>> library.\n");
>> > return EINVAL;
>>
>> > }
>>
>> > }
>>
>> > if (thread_in_trace) {
>>
>> > return cond_signal(condition);
>>
>> > }
>>
>> >
>>
>> > thread_in_trace = 1;
>>
>> > tracepoint(lttng_ust_pthread, pthread_cond_signal_begin, condition,
>>
>> > LTTNG_UST_CALLER_IP());
>>
>> > retval = cond_signal(condition);
>>
>> > tracepoint(lttng_ust_pthread, pthread_cond_signal_end, condition,
>>
>> > LTTNG_UST_CALLER_IP());
>>
>> > thread_in_trace = 0;
>>
>> > return retval;
>>
>> > }
>>
>> >
>>
>> > int pthread_cond_broadcast(pthread_cond_t *condition)
>>
>> > {
>>
>> > static int (*cond_broadcast)(pthread_cond_t *);
>>
>> > int retval;
>>
>> >
>>
>> > if (!cond_broadcast) {
>>
>> > cond_broadcast = dlsym(RTLD_NEXT, "pthread_cond_broadcast");
>>
>> > if (!cond_broadcast) {
>>
>> > if (thread_in_trace) {
>>
>> > abort();
>>
>> > }
>>
>> > fprintf(stderr, "unable to initialize pthread wrapper
>> library.\n");
>> > return EINVAL;
>>
>> > }
>>
>> > }
>>
>> > if (thread_in_trace) {
>>
>> > return cond_broadcast(condition);
>>
>> > }
>>
>> >
>>
>> > thread_in_trace = 1;
>>
>> > tracepoint(lttng_ust_pthread, pthread_cond_broadcast_begin,
>> condition,
>> > LTTNG_UST_CALLER_IP());
>>
>> > retval = cond_broadcast(condition);
>>
>> > tracepoint(lttng_ust_pthread, pthread_cond_broadcast_end, condition,
>>
>> > LTTNG_UST_CALLER_IP());
>>
>> > thread_in_trace = 0;
>>
>> > return retval;
>>
>> > }
>>
>> > _______________________________________________
>> > lttng-dev mailing list
>> > lttng-dev at lists.lttng.org
>> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>
>>
>> --
>> Jonathan Rajotte-Julien
>> EfficiOS
>>
>
>
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