Using "-c" and CTRL+C

[Bud Millwood]

Hi Dmitry, thanks for replying:

I'm not using the -l1 option. I see this behavior on both Ubuntu
12.10/x86-64 and CentOS 6.3/x86-64.

If I kill the target process, it always works correctly. The problem is if
I use CTRL-C to detach from the target process. Eventually I managed to get
it to produce the statistical output, as shown below. I used it for a few
hours, then left the terminal open over night, and the next day it was not
printing the output again. So it looks like this:

$ sudo strace -p 31457 -c
Process 31457 attached - interrupt to quit
^CProcess 31457 detached
$ sudo strace -p 31457 -c
Process 31457 attached - interrupt to quit
^CProcess 31457 detached
$ sudo strace -c -p 31457  <-- NOTE CHANGING COMMAND LINE ARGS ORDER
Process 31457 attached - interrupt to quit
^CProcess 31457 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 75.38    0.047831          66       730           poll
 24.62    0.015622          20       793           sendto
  0.00    0.000000           0        39           ioctl
  0.00    0.000000           0        39           select
  0.00    0.000000           0       769           recvfrom
  0.00    0.000000           0       107        29 futex
------ ----------- ----------- --------- --------- ----------------
100.00    0.063453                  2477        29 total

After this it worked for a while *regardless* of the order of the command
line arguments. And then after 24 hours, it doesn't work again at all,
*regardless* of command line argument order. So I just can't reproduce it
reliably.

- I thought it might be because there were no system calls in the target
process - that the target was blocked in one call, such as "select", but
that's not the case.
- I tried sending SIGINT and SIGTERM to the strace process from another
terminal, both signals cause the process to simply exit the same as if I
pressed CTRL-C, i.e. no data printed.

- Bud





On Thu, May 8, 2014 at 11:11 PM, Dmitry V. Levin <ldv at altlinux.org> wrote:

> Hi,
>
> On Wed, May 07, 2014 at 04:54:40PM +0200, Bud Millwood wrote:
> > Hi all, I'm not on this list but I'll keep an eye out for a response
> > to this message.
> >
> > In the past I noticed that if I ran "strace -c" against a process, I
> > could press CTRL-C and strace would print out the statistics it had
> > collected so far, then exit. It now seems to just exit without
> > printing any of the statistics.
>
> Strange, it works for me, both in simple and in -p mode.
> For example:
>
> $ strace -c cat & sleep 1 && kill -INT $!
> [1] 19981
> Process 19985 detached
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
> $  27.65    0.000060           8         8           mmap
>  14.29    0.000031           8         4           mprotect
>  10.14    0.000022           6         4           fstat
>   7.83    0.000017           9         2           open
>   7.83    0.000017           4         4           brk
>   6.45    0.000014           7         2         1 read
>   5.53    0.000012          12         1         1 access
>   5.07    0.000011           6         2           fadvise64
>   4.61    0.000010           5         2           close
>   4.61    0.000010          10         1           munmap
>   3.69    0.000008           8         1           execve
>   2.30    0.000005           5         1           arch_prctl
> ------ ----------- ----------- --------- --------- ----------------
> 100.00    0.000217                    32         2 total
> [1]+  Done                    strace -c cat
>
> $ sleep 2 && sleep 2 & sleep 1; strace -cp $! & sleep 2 && kill -INT $!
> [1] 19986
> [2] 19989
> Process 19986 attached
> Process 19986 detached
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
> $  80.77    0.000710         355         2         1 wait4
>  15.81    0.000139         139         1           clone
>   2.62    0.000023           4         6           rt_sigprocmask
>   0.46    0.000004           2         2           rt_sigaction
>   0.34    0.000003           3         1           rt_sigreturn
> ------ ----------- ----------- --------- --------- ----------------
> 100.00    0.000879                    12         1 total
> [2]+  Done                    strace -cp $!
> [1]-  Done                    sleep 2 && sleep 2
>
> You aren't using -I1 option, are you?
>
>
> --
> ldv
>
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