Retrive the information for a address using gdb

Question

Upon Running strace on a Java Application I notice some long time the syscall(mostly futex).

futex(0x7f8578001fd4, FUTEX_WAIT_PRIVATE, 1311, NULL) = 0 <15.082094> 

I really want to understand the wait on futex is for which shared resources over here.

But, I'm not sure how?

I did some googling and found GDB can be helpful for finding the above cause. But unfortunately, I'm not much aware of GDB as I had barely used it before.

Can some help me understand how to find the answer that I'm looking at.

Answer 1

The futex operation is waiting for another thread to release a lock. You should first look at Java-aware tools to see if this is a high-level Java lock. Perhaps even sending SIGQUIT (by pressing Ctrl+\\ is sufficient) for that.