Git hangs on clone

[Paul Alesius <paul@unnservice.com>]

80 out of 100 times git will hang indefinitely during a clone operation.
Here's the state of things during the hangs:


----------------------- scenario 1:
remote: Counting objects: 306395, done.
remote: Compressing objects: 100% (47753/47753), done.
remote: Total 306395 (delta 259044), reused 305469 (delta 258264)
Receiving objects: 100% (306395/306395), 207.20 MiB | 5.80 MiB/s, done.
Resolving deltas: 100% (259044/259044), done.
----------------------- ps aux | grep git:
build    28122  0.1  0.0 126032  2092 pts/1    Sl+  04:19   0:00 git clone
git://git.gnome.org/gtk+
---------------------- backtrace for scenario 1:
(gdb) bt
#0  0x0000003c9ee08e60 in pthread_join (threadid=47144800229120,
thread_return=thread_return@entry=0x7fff19edc928) at pthread_join.c:93
#1  0x00000000004cb6ab in finish_async (async=async@entry=0x7fff19edca00) at
run-command.c:739
#2  0x0000000000428318 in get_pack (pack_lockfile=0x121df80, xd=0x121dfc0)
at builtin/fetch-pack.c:773
#3  do_fetch_pack (pack_lockfile=0x121df80, match=0x125e0a0, nr_match=544,
orig_ref=<optimized out>, fd=0x121dfc0) at builtin/fetch-pack.c:835
#4  fetch_pack (my_args=my_args@entry=0x7fff19edd1b0, fd=fd@entry=0x121dfc0,
conn=<optimized out>, ref=<optimized out>, dest=dest@entry=0x1217e70
"git://git.gnome.org/gtk+",
    nr_heads=nr_heads@entry=544, heads=heads@entry=0x125e0a0,
pack_lockfile=pack_lockfile@entry=0x121df80) at builtin/fetch-pack.c:1090
#5  0x00000000004de08e in fetch_refs_via_pack (transport=0x121df20,
nr_heads=544, to_fetch=0x125c880) at transport.c:549
#6  0x00000000004e0472 in transport_fetch_refs
(transport=transport@entry=0x121df20, refs=refs@entry=0x123d3c0) at
transport.c:1167
#7  0x000000000041cbce in cmd_clone (argc=<optimized out>, argv=<optimized
out>, prefix=<optimized out>) at builtin/clone.c:859
#8  0x00000000004057d8 in run_builtin (argv=0x7fff19edd900, argc=2,
p=0x74a040) at git.c:308
#9  handle_internal_command (argc=2, argv=0x7fff19edd900) at git.c:468
#10 0x0000000000404be2 in run_argv (argv=0x7fff19edd790,
argcp=0x7fff19edd79c) at git.c:514
#11 main (argc=2, argv=0x7fff19edd900) at git.c:589
----------------------




---------------------- scenario 2:
remote: Counting objects: 306395, done.
remote: Compressing objects: 100% (47753/47753), done.
Receiving objects:  99% (303332/306395), 205.18 MiB | 452 KiB/s
----------------------- ps aux | grep git:
build    28247  0.5  0.0 126032  2088 pts/1    Sl+  04:30   0:00 git clone
git://git.gnome.org/gtk+
build    28249  8.4  0.3 144908 30480 pts/1    S+   04:30   0:12 git
index-pack --stdin -v --fix-thin --keep=fetch-pack 28247 on mydomain
---------------------- backtrace for scenario 1:
#0  0x0000003c9ee0e0ad in read () at ../sysdeps/unix/syscall-template.S:82
#1  0x00000000004ea29f in read (__nbytes=46, __buf=0x7fffeb4d8cc0, __fd=7)
at /usr/include/bits/unistd.h:45
#2  xread (fd=fd@entry=7, buf=buf@entry=0x7fffeb4d8cc0, len=len@entry=46) at
wrapper.c:142
#3  0x00000000004ea38b in read_in_full (fd=7, buf=buf@entry=0x7fffeb4d8cc0,
count=count@entry=46) at wrapper.c:171
#4  0x00000000004ad78c in index_pack_lockfile (ip_out=<optimized out>) at
pack-write.c:298
#5  0x00000000004285d4 in get_pack (pack_lockfile=0x1928f80, xd=0x1928fc0)
at builtin/fetch-pack.c:767
#6  do_fetch_pack (pack_lockfile=0x1928f80, match=0x19690a0, nr_match=544,
orig_ref=<optimized out>, fd=0x1928fc0) at builtin/fetch-pack.c:835
#7  fetch_pack (my_args=my_args@entry=0x7fffeb4da580, fd=fd@entry=0x1928fc0,
conn=<optimized out>, ref=<optimized out>, dest=dest@entry=0x1922e70
"git://git.gnome.org/gtk+",
    nr_heads=nr_heads@entry=544, heads=heads@entry=0x19690a0,
pack_lockfile=pack_lockfile@entry=0x1928f80) at builtin/fetch-pack.c:1090
#8  0x00000000004de08e in fetch_refs_via_pack (transport=0x1928f20,
nr_heads=544, to_fetch=0x1967880) at transport.c:549
#9  0x00000000004e0472 in transport_fetch_refs
(transport=transport@entry=0x1928f20, refs=refs@entry=0x19483c0) at
transport.c:1167
#10 0x000000000041cbce in cmd_clone (argc=<optimized out>, argv=<optimized
out>, prefix=<optimized out>) at builtin/clone.c:859
#11 0x00000000004057d8 in run_builtin (argv=0x7fffeb4dacd0, argc=2,
p=0x74a040) at git.c:308
#12 handle_internal_command (argc=2, argv=0x7fffeb4dacd0) at git.c:468
#13 0x0000000000404be2 in run_argv (argv=0x7fffeb4dab60,
argcp=0x7fffeb4dab6c) at git.c:514
#14 main (argc=2, argv=0x7fffeb4dacd0) at git.c:589
----------------------



---------------------- facts:
- Happens on multiple machines on this LAN, which made me believe it's the
NAT router.
- Happens when using any repository.
- There's nothing filtering egress ports (Other than the NAT)
- Kernel 3(?) to 3.5 which I run currently
- I often see it hang at __read_nocancel too in the backtrace, which is part
of the read()
- I have to abort the clone operation and retry indefinitely until it works,
which may be never.




- Paul