On Mon, Aug 4, 2014 at 6:37 PM, Richard Tollerton <rich.toller...@ni.com> wrote: > Otavio Salvador <ota...@ossystems.com.br> writes: > >> On Mon, Aug 4, 2014 at 6:18 PM, Richard Tollerton <rich.toller...@ni.com> >> wrote: >>> Otavio Salvador <ota...@ossystems.com.br> writes: >>> >>>> I am not sure about this one. I see the value you are adding here but >>>> I worry how often something can be connected during this process and >>>> change the contents along the way. Did you see something as that >>>> during your tests? >>> >>> No, but point taken. I didn't really test "physical" hotplug during >>> bootup -- and in particular, for this to be a persisting issue, the >>> added/removed device must be removed/added during this boot -- but I >>> suppose that is totally possible. >>> >>> This reflects an underlying race condition, starting at the computation >>> of NEWDATA/OLDDATA in the udev initscript, and ending in the tarball >>> creation in udev-cache. I suppose that we can mitigate this by spinning >>> in udev-cache until the devcache stops changing...? Cheesy, untested, >>> dirty RFC follows: >> >> You need to check the list of files taken by 'tar' and compare. This >> mitigates it but does not really solves the issue. > > Hmm, I'm confused. If we relied entirely on /dev contents, how would we > detect (and correct for) if a device was removed between the execution > of udev and of udev-cache? > >> Maybe we could "copy" the nodes to a tmp area and use this as a >> snapshot? The copy should be fast and makes it mostly "atomic". > > I agree that the copy of the contents of /dev needs to be as fast as > possible -- your about using tmpfs as a staging area is well taken. But > beyond that, it seems to me that the root issue you articulated is about > ensuring adequate synchronization of udev.cache and the tarball; > rereading CMP_FILE_LIST in udev-cache thus seems unavoidable.
Yes, that's why I think we need: - copy contents to a staging area - generate the tarball This way we avoid the following steps: - generate the list of contents - generate the tarball - generate tarball's contents - compare, loop if does not match. Makes sense? -- Otavio Salvador O.S. Systems http://www.ossystems.com.br http://code.ossystems.com.br Mobile: +55 (53) 9981-7854 Mobile: +1 (347) 903-9750 -- _______________________________________________ Openembedded-core mailing list Openembedded-core@lists.openembedded.org http://lists.openembedded.org/mailman/listinfo/openembedded-core
