[CRIU] [PATCH v2] tests: fix builds on alpine and centos

[Dmitry Safonov]

2018-06-26 18:00 GMT+01:00 Adrian Reber <areber at redhat.com>:
> On Tue, Jun 26, 2018 at 09:37:08AM -0700, Andrei Vagin wrote:
>> On Tue, Jun 26, 2018 at 08:24:08AM +0200, Adrian Reber wrote:
>> > On Thu, Jun 21, 2018 at 11:39:19PM +0200, Adrian Reber wrote:
>> > > On Thu, Jun 21, 2018 at 02:35:38PM -0700, Andrei Vagin wrote:
>> > > > On Thu, Jun 21, 2018 at 09:10:38PM +0000, Adrian Reber wrote:
>> > > > > From: Adrian Reber <areber at redhat.com>
>> > > > >
>> > > > > Install sudo, create test user with ID 1000, install bash,
>> > > > > fix pidfile creation and pidfile chmod.
>> > > > >
>> > > > > v2:
>> > > > >  * use sleep to give the criu daemon some time to start up
>> > > >
>> > > > Can we use --status-fd? It is designed for this.
>> > >
>> > > Oh, very good idea. Thanks. I will try that.
>> >
>> > Just to let you know. I have problems reading the result from the
>> > status_fd on all our different travis targets. It works for most shells,
>> > but not all of them. Still trying to understand how to correctly solve
>> > this, so that it works everywhere.
>>
>> We already install bash in all docker containers, so you can create a
>> bash script.
>
> I currently have the problem that 'read -n 1' hangs on Ubuntu and it is
> not clear why. I have the following test case:
>
> bash -c 'rm -f status; mkfifo status; exec 201<>status;  ./a.out 201; read -n1 -u 201'
>
> The test program a.out (great name) is really simple:
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main(int argc, char *argv[])
> {
>         int status_fd;
>         char c = 0;
>         int r;
>
>         status_fd = atoi(argv[1]);
>
>         printf("status_fd %d\n", status_fd);
>         r = write(status_fd, &c, 1);
>         printf("write %d\n", r);
> }
>
> And strace tells me the following:
>
> fcntl(201, F_GETFD)                     = 0
> ioctl(201, TCGETS, 0x7ffd97626ad0)      = -1 ENOTTY (Inappropriate ioctl for device)
> lseek(201, 0, SEEK_CUR)                 = -1 ESPIPE (Illegal seek)
> read(201, "\0", 1)                      = 1
> read(201,
>
> On CentOS and alpine it does not hang and I get the following:
>
> fcntl(201, F_GETFD)                     = 0
> ioctl(201, TCGETS, 0x7ffeeb6ee6a0)      = -1 ENOTTY (Inappropriate ioctl for device)
> lseek(201, 0, SEEK_CUR)                 = -1 ESPIPE (Illegal seek)
> read(201, "\0", 1)                      = 1
> exit_group(0)                           = ?
>
> So on Ubuntu, for some reason, 'read -n 1' does not stop after reading a
> single byte from the pipe and that seems to be the problem I have in
> travis.
>
> Can you reproduce this behavior? Do you have an idea why this is
> happening? I am doing something wrong? I am already looking at the code
> for a few days and it is not clear what is happening here.

It looks like, `read' bash command doesn't count zero-bytes with -n.

> char c = 0;

-- 
             Dmitry