Random serf checkout failures

I've been experimenting checking out subversion/tags from my local
mirror of the Subversion repository using a client and mod_dav_svn from
trunk. I'm getting several different errors seemingly at random, I
suspect they may be related to some common underlying problem.

Sometimes I see a checksum error such as this:

../src/subversion/svn/checkout-cmd.c:168: (apr_err=200014)
../src/subversion/libsvn_client/checkout.c:179: (apr_err=200014)
../src/subversion/libsvn_client/update.c:579: (apr_err=200014)
../src/subversion/libsvn_client/update.c:440: (apr_err=200014)
../src/subversion/libsvn_wc/adm_crawler.c:858: (apr_err=200014)
../src/subversion/libsvn_ra_serf/update.c:2515: (apr_err=200014)
../src/subversion/libsvn_ra_serf/util.c:2023: (apr_err=200014)
../src/subversion/libsvn_ra_serf/util.c:2004: (apr_err=200014)
../src/subversion/libsvn_ra_serf/update.c:1065: (apr_err=200014)
../src/subversion/libsvn_ra_serf/update.c:895: (apr_err=200014)
../src/subversion/libsvn_wc/update_editor.c:3919: (apr_err=200014)
../src/subversion/libsvn_subr/checksum.c:469: (apr_err=200014)
svn: E200014: Checksum mismatch for '/home/pm/sw/subversion/obj/wc/0.25.0/subversion/libsvn_fs/tree.c':
   expected: c38c3e8df15f36a45b8a626e4d82a25d
     actual: 2532722e781ef9afe673c89fd467d5f0

The expected checksum is the checksum in the repository. It's a
different file each time this error occurs.

Another error is an assert:

Program received signal SIGABRT, Aborted.
0x00007ffff6530425 in __GI_raise (sig=<optimised out>)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
64 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0 0x00007ffff6530425 in __GI_raise (sig=<optimised out>)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1 0x00007ffff6533b8b in __GI_abort () at abort.c:91
#2 0x00007ffff6d41b78 in svn_error_abort_on_malfunction (can_return=1,
    file=0x7ffff5a97058 "../src/subversion/libsvn_ra_serf/update.c", line=673,
    expr=0x7ffff5a970fe "! dir->ref_count")
    at ../src/subversion/libsvn_subr/error.c:678
#3 0x00007ffff6d41bcc in svn_error__malfunction (can_return=1,
    file=0x7ffff5a97058 "../src/subversion/libsvn_ra_serf/update.c", line=673,
    expr=0x7ffff5a970fe "! dir->ref_count")
    at ../src/subversion/libsvn_subr/error.c:703
#4 0x00007ffff5a85d50 in close_all_dirs (dir=0x7fffe885f0c8)
    at ../src/subversion/libsvn_ra_serf/update.c:673
#5 0x00007ffff5a85cda in close_all_dirs (dir=0x7fffe88d00c8)
    at ../src/subversion/libsvn_ra_serf/update.c:669
#6 0x00007ffff5a85cda in close_all_dirs (dir=0x7fffe89860c8)
    at ../src/subversion/libsvn_ra_serf/update.c:669
#7 0x00007ffff5a85cda in close_all_dirs (dir=0x7ffff7f2a0c8)
    at ../src/subversion/libsvn_ra_serf/update.c:669
#8 0x00007ffff5a8b01b in finish_report (report_baton=0x7ffff7fb8060,
    pool=0x7ffff7fb5028) at ../src/subversion/libsvn_ra_serf/update.c:2665
#9 0x00007ffff76945cc in svn_wc_crawl_revisions5 (wc_ctx=0x7ffff7f670e0,
    local_abspath=0x7ffff7fb5168 "/home/pm/sw/subversion/obj/wc",
    reporter=0x7ffff5ca07c0, report_baton=0x7ffff7fb8060, restore_files=1,
    depth=svn_depth_unknown, honor_depth_exclude=1,
    depth_compatibility_trick=0, use_commit_times=0,
    cancel_func=0x416b1b <svn_cl__check_cancel>, cancel_baton=0x0,
    notify_func=0x41c703 <notify>, notify_baton=0x7ffff7f673d0,
    scratch_pool=0x7ffff7fb5028)
    at ../src/subversion/libsvn_wc/adm_crawler.c:858

This appears to be in the end of the checkout code but the working copy
is far from complete.

I have also seen this error:

../src/subversion/svn/checkout-cmd.c:168: (apr_err=175009)
../src/subversion/libsvn_client/checkout.c:179: (apr_err=175009)
../src/subversion/libsvn_client/update.c:579: (apr_err=175009)
../src/subversion/libsvn_client/update.c:440: (apr_err=175009)
../src/subversion/libsvn_wc/adm_crawler.c:858: (apr_err=175009)
../src/subversion/libsvn_ra_serf/update.c:2515: (apr_err=175009)
../src/subversion/libsvn_ra_serf/util.c:2028: (apr_err=175009)
../src/subversion/libsvn_ra_serf/util.c:1850: (apr_err=175009)
svn: E175009: Premature EOF seen from server (http status=200)
../src/subversion/libsvn_ra_serf/util.c:1850: (apr_err=70014)
svn: E070014: End of file found

All of these look like some problem with the data transfer, serf losing
data or mod_dav_svn not sending it, but I suppose they could also be
caused by memory corruption. These errors generally occur when there
are thousands of files in the pristine store and tens of thousands of
files in the working copy.

I've seen these error while checking out across my LAN and on localhost
so I don't think it can be network problem. I'm using serf 1.1.x_at_1674
and subversion/mod_dav_svn from trunk (currently r1404529 but I was
seeing these errors a couple of weeks ago as well). I'm seeing these
errors on Debian/stable and Ubuntu/12.04.

-- 
Philip