Re: misc/tst-ttyname time outs

[Carlos O'Donell <carlos at redhat dot com>]

On 1/2/19 9:48 AM, Florian Weimer wrote:
> * Szabolcs Nagy:
> 
>> in run_chroot_tests the following loop time outs for me:
>>
>>     /* keep creating PTYs until we we get a name collision */
>>     while (stat (slavename, &st) < 0)
>>       posix_openpt (O_RDWR|O_NOCTTY|O_NONBLOCK);
>>
>> it seems posix_openpt can fail with EMFILE or ENOSPC in the
>> loop and then it never finishes.
>>
>> example strace:
>> [pid 24510] newfstatat(AT_FDCWD, "/dev/pts/1789", 0xffffdd528fe0, 0) = -1 ENOENT (No such file or directory)
>> [pid 24510] openat(AT_FDCWD, "/dev/ptmx", O_RDWR|O_NOCTTY|O_NONBLOCK) = -1 ENOSPC (No space left on device)
>> [pid 24510] newfstatat(AT_FDCWD, "/dev/pts/1789", 0xffffdd528fe0, 0) = -1 ENOENT (No such file or directory)
>> [pid 24510] openat(AT_FDCWD, "/dev/ptmx", O_RDWR|O_NOCTTY|O_NONBLOCK) = -1 ENOSPC (No space left on device)
>> [pid 24510] newfstatat(AT_FDCWD, "/dev/pts/1789", 0xffffdd528fe0, 0) = -1 ENOENT (No such file or directory)
>> ...
>>
>> i'm not sure what can cause such failures, but it happens
>> regularly on the aarch64 build bot instance recently, let
>> me know if somebody knows how to make that loop or the
>> runtime environment more reliable.
> 
> I think we should detect that posix_openpt fails and treat ENOSPC,
> EMFILE, ENFILE as unsupported, along with an error message that we could
> not create a PTY collision for slavename.  Other error should result in
> a hard failure.
> 
> I can write a patch if you are able to test it.

I agree that's the best option. You should just checkin a fix, it's
obvious that if we're failing with ENOSPC, EMFILE, or ENFILE that we're
unable to complete the test.

However, I would add another requirement:

* Print an message indicating possible ways in which this can be fixed
  to work.

For example, should we try to determine what needs fixing and print an
appropriate informative message?

-- 
Cheers,
Carlos.