CODEWITHSUNDEEP
cmemory-leakspthreads
Sterling
Sterling

Reputation: 4223

pthread_create memory leak?

Whenever I run valgrind on my program, it is telling that I have possibly lost memory wherever I call pthread_create. I have been trying to follow the guidance on

valgrind memory leak errors when using pthread_create http://gelorakan.wordpress.com/2007/11/26/pthead_create-valgrind-memory-leak-solved/

and other various websites google gave me, but nothing has worked. So far I have tried joining the threads, setting an pthread_attr_t to DETACHED, calling pthread_detach on each thread, and calling pthread_exit().

trying PTHREAD_CREATE_DETACHED - 

pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

pthread_create(&c_udp_comm, &attr, udp_comm_thread, (void*)this);
pthread_create(&drive, &attr, driving_thread, (void*)this);
pthread_create(&update, &attr, update_server_thread(void*)this);

I think I may have coded this next one with joining wrong...I am going by https://computing.llnl.gov/tutorials/pthreads/ and they have all their threads in an array so they just for loop. But I don't have them all in an array so I tried to just change it to work. Please tell me if I did it wrong.

void* status;
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

pthread_create(&c_udp_comm, &attr, udp_comm_thread, (void*)this);
pthread_create(&drive, &attr, driving_thread, (void*)this);
pthread_create(&update, &attr, update_server_thread(void*)this);

pthread_join(c_udp_comm, &status);
pthread_join(drive, &status);
pthread_join(update, &status);

trying pthread_detach - 

pthread_create(&c_udp_comm, NULL, udp_comm_thread, (void*)this);
pthread_create(&drive, NULL, driving_thread, (void*)this);
pthread_create(&update, NULL, update_server_thread(void*)this);

pthread_detach(c_udp_comm);
pthread_detach(drive);
pthread_detach(update);

trying pthread_exit - 

pthread_create(&c_udp_comm, NULL, udp_comm_thread, (void*)this);
pthread_create(&drive, NULL, driving_thread, (void*)this);
pthread_create(&update, NULL, update_server_thread(void*)this);

pthread_exit(NULL);

If anyone can help me figure out why none of this is working I would be very grateful.

Upvotes: 3

Views: 2783

Answers (2)

David Schwartz
David Schwartz

Reputation: 182893

You can prove there's no leak by taking your code that uses pthread_join and repeating the create/join process a few times. You'll see that the amount of memory "leaked" does not change, proving that no memory was actually leaked at all.

Upvotes: 2

R.. GitHub STOP HELPING ICE
R.. GitHub STOP HELPING ICE

Reputation: 215647

glibc doesn't free thread stacks when threads exit; it caches them for reuse, and only prunes the cache when it gets huge. Thus it always "leaks" some memory.

Upvotes: 5

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