program crashed with EPIPE while without core dump

fantasy1215 · 06-07-2013, 03:39 AM

I use strace to watch a running program, and catch the information when the program crashed. Now I paste the strace information as follow:

Code:

9134  select(8, NULL, [7], NULL, {2, 0}) = 1 (out [7], left {2, 0})
9134  write(7, "V\0                              "..., 88) = -1 EPIPE (Broken pipe)
9134  --- SIGPIPE (Broken pipe) @ 0 (0) ---
8858  <... msgrcv resumed> 98307, {1749233712, ": 33 30 30 31 30 30 34 31 33 35 "...}, 2048, 0, 0) = ? ERESTARTNOHAND (To be restarted)
8859  <... futex resumed> )             = -1 EINTR (Interrupted system call)
8858  +++ killed by SIGPIPE +++
8859  +++ killed by SIGPIPE +++
10080 <... futex resumed> )             = -1 EINTR (Interrupted system call)
8856  <... select resumed> )            = ? ERESTARTNOHAND (To be restarted)
10080 +++ killed by SIGPIPE +++
8856  +++ killed by SIGPIPE +++

I have questions:
1. Why would the EPIPE occur?
2. How could I fix this problem?
3. Why wouldn't it generate a coredump?(I've set ulimit -c unlimited already)

Edit: After I googled broken pipe, I add signal(SIGPIPE, SIG_IGN); to my program, But my program still crashed by EPIPE (Broken pipe). This is a socket server program.

And the thread I googled is http://www.unix.com/programming/1633...ogramming.html

pan64 · 06-07-2013, 04:01 AM

sigpipe or broken pipe means the communication channel (the pipe itself) has been destroyed. Usually it caused because the other side (the app) died, therefore no app can handle the communication.
So usually either stdin or stdout is redirected to/from another app, but there can be other situation as well.
It will not cause core, it has no meaning in this case. You need to find the other end of the pipe and check that app.

NevemTeve · 06-07-2013, 04:37 AM

For non-trivial programs (meaning: that handle error conditions on write), add this:

Code:

signal (SIGPIPE, SIG_IGN);

ta0kira · 06-07-2013, 08:49 AM

Quote:

Originally Posted by NevemTeve

For non-trivial programs (meaning: that handle error conditions on write), add this:

Code:

signal (SIGPIPE, SIG_IGN);

Additionally, this makes EPIPE a possible errno value for a failed write operation, which might need to be considered separately from the other possible errors.

Quote:

Originally Posted by fantasy1215

3. Why wouldn't it generate a coredump?(I've set ulimit -c unlimited already)

If you look at man 7 signal, it says that SIGPIPE results in termination rather than a core dump, presumably since there isn't a real need to perform a backtrace.

Kevin Barry

fantasy1215 · 06-07-2013, 07:14 PM

Quote:

Originally Posted by NevemTeve

For non-trivial programs (meaning: that handle error conditions on write), add this:

Code:

signal (SIGPIPE, SIG_IGN);

Now I've added signal (SIGPIPE, SIG_IGN); already to my program, but the program still gets crashed by EPIPE.

ta0kira · 06-07-2013, 10:19 PM

Quote:

Originally Posted by fantasy1215

Now I've added signal (SIGPIPE, SIG_IGN); already to my program, but the program still gets crashed by EPIPE.

That's a problem with how you handle EPIPE, then. If you want the program to continue, close the descriptor that had the EPIPE and set a flag that indicates that output should be skipped.

Kevin Barry

NevemTeve · 06-08-2013, 04:31 AM

> Now I've added signal (SIGPIPE, SIG_IGN); already to my program, but the program still gets crashed by EPIPE.

1. What does strace show?
2. And gdb?

3. Your program seems to be multi-thread (or multi-proces?), try using 'signal' right before the write.

pan64 · 06-08-2013, 05:09 AM

Why don't you try to catch the other side? You saw write(7, "V\0 "..., 88) = -1 EPIPE (Broken pipe), so you need to check how it (file descriptor = 7) was opened and why it was dropped (died ??)

fantasy1215 · 06-08-2013, 05:27 AM

Quote:

Originally Posted by NevemTeve

> Now I've added signal (SIGPIPE, SIG_IGN); already to my program, but the program still gets crashed by EPIPE.

1. What does strace show?
2. And gdb?

3. Your program seems to be multi-thread (or multi-proces?), try using 'signal' right before the write.

Thanks for your reply, and the strace message showed still as the same as before.