Re: [dpdk-dev] pthread_barrier_deadlock in -rc1

[Tan, Jianfeng]

Hi Maxime and Olivier,

[...]
Below patch can fix another strange sigsegv issue in my VM. Please check
if it works for you. I doubt it's use-after-free problem which could
lead to different issues in different env. Please have a try.

diff --git a/lib/librte_eal/common/eal_common_thread.c
b/lib/librte_eal/common/eal_common_thread.c
index de69452..d91b67d 100644
--- a/lib/librte_eal/common/eal_common_thread.c
+++ b/lib/librte_eal/common/eal_common_thread.c
@@ -205,6 +205,7 @@ rte_ctrl_thread_create(pthread_t *thread, const char
*name,
                  goto fail;

          pthread_barrier_wait(&params->configured);
+       pthread_barrier_destroy(&params->configured);
Thanks Jianfeng, that fixes my issue.
For correctness, I wonder whether we should check pthread_barrier_wait
return, and only call destroy() if PTHREAD_BARRIER_SERIAL_THREAD?
And so also do same the same thing in rte_thread_init().

What do you think?
Thanks,
Maxime

Thanks for the update. I also have a patch that replaces the barrier by
a lock which could also work, but if Jianfeng's one fixes the issue, I
think it is better.

About the PTHREAD_BARRIER_SERIAL_THREAD, not sure it will change
something:

        Upon successful completion, the pthread_barrier_wait() function
        shall return PTHREAD_BARRIER_SERIAL_THREAD for a single
        (arbitrary) thread synchronized at the barrier and zero for each
        of the other threads. Otherwise, an error number shall be
        returned to indicate the error.

I understand that it will ensure that only one barrier will return
PTHREAD_BARRIER_SERIAL_THREAD, but not necessarily the last one. So
if destroy() is called in the parent thread, it should be the same, no?

By the way, there is also a small memory leak that was introduced by
the previous patch, maybe you can add the fix too:

-       if (ret != 0)
+       if (ret != 0) {
+               free(params);
                 return ret;
+       }

How about: the thread who gets PTHREAD_BARRIER_SERIAL_THREAD returned, 
is responsible for the destroy and free(params)?

Thanks,
Jianfeng