Hi Jon,
I have logged your patch into the issue tracker, 3546;
http://subversion.tigris.org/issues/show_bug.cgi?id=3546
Gavin
On 28/11/2009, at 06:53 , Jon Foster wrote:
> Hi,
>
> This fixes the race condition where two svnsync processes can lock
> the repository at the same time (as noticed by Stefan Sperling
> earlier today). I wanted to do this without changing the RA layer,
> so that it can work with older servers.
>
> Since the RA layer doesn't have a test-and-set primitive (other
> than a commit!), some raciness is inevitable. This patch fixes the
> dangerous race, but introduces a much less dangerous race. With
> this patch, two "svnsync" processes trying to lock the repository at
> the same time might both fail to get the lock. To mitigate this,
> both processes will sleep for a random amount of time before
> retrying. This should reduce the chance of them staying in lock-step
> and repeatedly failing. (Hopefully the chance becomes negligible).
>
> This doesn't conflict with my --use-external-locking patch from
> earlier today; they change different parts of the code and have
> different use-cases.
>
> [[[
> Fix race condition that allowed two svnsync processes to get the lock
> at the same time.
>
> * subversion/include/svn_props.h:
> (SVNSYNC_PROP_PRE_LOCK_PREFIX): New define.
>
> * subversion/svnsync/main.c:
> (get_local_host_name, generate_moderately_random_number,
> try_get_lock): New functions.
> (get_lock): Rewritten.
>
> Found by: stsp
> Jon Foster <jon.foster_at_cabot.co.uk>
> (Independently discovered)
> Patch by: Jon Foster <jon.foster_at_cabot.co.uk>
> ]]]
>
> Apologies for the .zip format - my mailserver is blocking outgoing
> .patch files.
>
> Kind regards,
>
> Jon Foster
>
>
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Received on 2009-12-09 10:02:28 CET