[OE-core] race condition... in cp?

[Chris Larson]

On Fri, Mar 16, 2012 at 4:35 AM, Paul Eggleton
<paul.eggleton at linux.intel.com> wrote:
> On Friday 16 March 2012 06:58:40 James Limbouris wrote:
>> Hi,
>>
>> I got a strange error when bitbaking two images after removing some files in
>> the deploy/images folder. It looks a whole lot like the cp's from the
>> individual tasks were racing... I didn't know this sort of thing could
>> happen.
>>
>> bitbake rica-dev-image rica-release-example-image
>> <...>
>> NOTE: Resolving any missing task queue dependencies
>> NOTE: multiple providers are available for runtime libssl
>> (openssl-nativesdk, openssl) NOTE: consider defining a PREFERRED_PROVIDER
>> entry to match libssl NOTE: Preparing runqueue
>> NOTE: Executing SetScene Tasks
>> NOTE: Executing RunQueue Tasks
>> NOTE: Running task 3673 of 3692 (ID: 23,
>> /home/james/oe/meta-rica5/recipes/images/rica-release-example-image.bb,
>> do_rootfs) NOTE: Running task 3685 of 3692 (ID: 8,
>> /home/james/oe/meta-rica5/recipes/images/rica-dev-image.bb, do_rootfs)
>> NOTE: package rica-release-example-image-1.0-r0: task do_rootfs: Started
>> NOTE: package rica-dev-image-1.0-r0: task do_rootfs: Started
>> ERROR: Function failed: do_rootfs (see
>> /home/james/oe/build/tmp-eglibc/work/rica5-rica-linux-gnueabi/rica-dev-imag
>> e-1.0-r0/temp/log.do_rootfs.4011 for further information) ERROR: Logfile of
>> failure stored in:
>> /home/james/oe/build/tmp-eglibc/work/rica5-rica-linux-gnueabi/rica-dev-imag
>> e-1.0-r0/temp/log.do_rootfs.4011
>> Log data follows:
>> | ERROR: Function failed: do_rootfs (see
>> | /home/james/oe/build/tmp-eglibc/work/rica5-rica-linux-gnueabi/rica-dev-im
>> | age-1.0-r0/temp/log.do_rootfs.4011 for further information) cp: cannot
>> | create regular file
>> | `/home/james/oe/build/tmp-eglibc/deploy/images/rica5/README_-_DO_NOT_DELE
>> | TE_FILES_IN_THIS_DIRECTORY.txt': File exists
>> NOTE: package rica-dev-image-1.0-r0: task do_rootfs: Failed
>> ERROR: Task 8 (/home/james/oe/meta-rica5/recipes/images/rica-dev-image.bb,
>> do_rootfs) failed with exit code '1' Waiting for 1 active tasks to finish:
>> 0: rica-release-example-image-1.0-r0 do_rootfs (pid 4008)
>> NOTE: package rica-release-example-image-1.0-r0: task do_rootfs: Succeeded
>> NOTE: Tasks Summary: Attempted 3685 tasks of which 3683 didn't need to be
>> rerun and 1 failed. pseudo: You must set the PSEUDO_PREFIX environment
>> variable to run pseudo. pseudo: You must set the PSEUDO_PREFIX environment
>> variable to run pseudo.
>>
>> Summary: 1 task failed:
>>   /home/james/oe/meta-rica5/recipes/images/rica-dev-image.bb, do_rootfs
>> Summary: There was 1 ERROR message shown, returning a non-zero exit code.
>>
>> Perhaps we should be using cp -f, or discarding the result?
>
> I tried to use -n originally, but apparently that's not a standard option we
> can expect to be available everywhere so it had to be removed. I think in this
> case the easiest thing to do is just ignore the failure since if it's genuine
> it's not catastrophic and also it's highly unlikely you won't get a subsequent
> failure elsewhere. I'll prepare a fix.

I had a fix for this, but apparently I never got it merged. As you
say, the easiest way is to ignore failure. You can't use -f, because
of how cp does its checking - the failure still occurs. And of course
you can't check for existence first, as that's a race. The fix I had
just used shell redirections (>) instead of cp, as they don't care if
the file already exists.
-- 
Christopher Larson