CPU spin in popen()

Asked Jan 06 '15 at 12:55

Active Jan 06 '15 at 12:55

Viewed 172 times

Here's my code piece:

FILE *f;
char cmd[4096] = {0};

snprintf(cmd, sizeof(cmd), "echo -n \"%s\" | openssl md5 -hex 2>/dev/null | sed 's/^.* //g'", input);
if (NULL == (f = popen(cmd, "r"))) {
    perror(popen);
}

I got cpu spin in popen() and here's my callstack:

#0  0xf54d21cc in ?? () from /lib/libpthread.so.0
#1  0xf4395eb3 in fork () from /lib/libc.so.6
#2  0xf435b1d9 in _IO_proc_open () from /lib/libc.so.6
#3  0xf435b525 in popen () from /lib/libc.so.6

I have no idea how this happened. Is there any "input" that could cause this happen?

asked Jan 06 '15 at 12:55

kai

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is the input sanitized? – Karoly Horvath Jan 06 '15 at 12:58
It looks like the `sed` command tries to do its best to reduce the output to a minimum. – joop Jan 06 '15 at 12:59
What happens when you run this on a plain commandline in parts and `time` every step, instead of piping everything into the next command? – Karel Kubat Jan 06 '15 at 13:31
you are calling `perror(popen);`, perhaps you want to say `perror("popen");`. – Luis Colorado Jan 08 '15 at 08:43

CPU spin in popen()

0 Answers0