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## Several developers simultaneously attempting to run CVS

If several developers try to run CVS at the same time, one may get the following message:

    [11:43:23] waiting for bach's lock in /usr/local/cvsroot/foo

CVS will try again every 30 seconds, and either continue with the operation or print the message again, if it still needs to wait. If a lock seems to stick around for an undue amount of time, find the person holding the lock and ask them about the cvs command they are running. If they aren't running a cvs command, look for and remove files starting with ``#cvs.tfl'`, ``#cvs.rfl'`, or ``#cvs.wfl'` from the repository.

Note that these locks are to protect CVS's internal data structures and have no relationship to the word lock in the sense used by RCS---which refers to reserved checkouts (see section Multiple developers).

Any number of people can be reading from a given repository at a time; only when someone is writing do the locks prevent other people from reading or writing.

One might hope for the following property

    If someone commits some changes in one cvs command,
    then an update by someone else will either get all the
    changes, or none of them.

but CVS does not have this property. For example, given the files

    a/one.c
    a/two.c
    b/three.c
    b/four.c

if someone runs

    cvs ci a/two.c b/three.c

and someone else runs `cvs update` at the same time, the person running `update` might get only the change to ``b/three.c'` and not the change to ``a/two.c'`.

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