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Re: Subversion's use of Berkeley DB [#11511]

From: Branko Čibej <brane_at_xbc.nu>
Date: 2004-12-09 23:11:22 CET

C. Michael Pilato wrote:

>Keith Bostic <bostic@abyssinian.sleepycat.com> writes:
>> As a springboard for that discussion, I propose we find a
>> serialization point for all threads of control using a
>> Subversion repository so we can determine if a thread of
>> control is the first thread of control entering the database
>> environment after a possible application or system failure.
>My suggestion is that libsvn_fs_base grows the same serialization that
>mod_db4 uses, which is based around the use of a shared memory segment
>with a reference count in it.
There is a pretty fundamental problem with using a reference count like
that. If a process that is accessing BDB crashes after having
incremented the refcount, the refcount is gets out if sync and is
useless. Also, other processes that are already running might wedge on a
lock owned by the crashed process. I see no way to resolve this.

-- Brane

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Received on Fri Dec 10 03:11:16 2004

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