Locking issue

[Sergio Villar Senin <svillar igalia com>]

Hi,

playing with message transfers stuff I found a locking issue regarding
the new folder monitor functionality. I think it's easy to understand
the locking problem with a backtrace, see how the lock in unload_folder
creates a deadlock because the folder was previously locked in the call
to tny_camel_folder_transfer_msgs_async_thread.

Br.

#0  unload_folder (priv=0x81eb368, destroy=0) at tny-camel-folder.c:246
#1  0xb7dfaf8d in tny_camel_folder_uncache (self=0x81eb358) at
tny-camel-folder.c:1998
#2  0xb7dfafae in _tny_camel_folder_check_uncache (self=0x81eb358,
priv=0x81eb368) at tny-camel-folder.c:2008
#3  0xb7df2e80 in tny_camel_header_finalize (object=0x82b6320) at
tny-camel-header.c:562
#4  0xb6e8d1ed in IA__g_object_unref (_object=0x82b6320) at gobject.c:1788
#5  0xb7b263d8 in destroy_item (item=0x82b6320, user_data=0x0) at
tny-simple-list.c:141
#6  0xb6dbf218 in IA__g_list_foreach (list=0xb41027c0, func=0xb7b26358
<destroy_item>, user_data=0x0)
    at glist.c:495
#7  0xb7b26450 in tny_simple_list_finalize (object=0x82b6308) at
tny-simple-list.c:153
#8  0xb6e8d1ed in IA__g_object_unref (_object=0x82b6308) at gobject.c:1788
#9  0xb7b21ed3 in tny_folder_change_finalize (object=0x82722f8) at
tny-folder-change.c:413
#10 0xb6e8d1ed in IA__g_object_unref (_object=0x82722f8) at gobject.c:1788
#11 0xb7df6348 in folder_changed (camel_folder=0x821e5e0,
info=0xb4104c58, user_data=0x81eb368)
    at tny-camel-folder.c:197
#12 0xb7d6996c in camel_object_trigger_event (vo=0x821e5e0,
name=0xb569ebe3 "folder_changed",
    event_data=0xb4104c58) at camel-object.c:1424
#13 0xb568d9e4 in camel_imap_folder_changed (folder=0x821e5e0,
exists=14, expunged=0x82b6508, ex=0xb4ad732c)
    at camel-imap-folder.c:3623
#14 0xb5687858 in imap_rescan (folder=0x821e5e0, exists=14,
ex=0xb4ad732c) at camel-imap-folder.c:1177
#15 0xb5686819 in camel_imap_folder_selected (folder=0x821e5e0,
response=0xb41052a8, ex=0xb4ad732c)
    at camel-imap-folder.c:618
#16 0xb5686d07 in imap_refresh_info (folder=0x821e5e0, ex=0xb4ad732c) at
camel-imap-folder.c:749
#17 0xb568907e in imap_append_online (folder=0x821e5e0,
message=0x8277ef8, info=0x82b6948,
    appended_uid=0xb4104038, ex=0xb4ad732c) at camel-imap-folder.c:1797
#18 0xb7da087c in disco_append_message (folder=0x821e5e0,
message=0x8277ef8, info=0x82b6948,
    appended_uid=0xb4104038, ex=0xb4ad732c) at camel-disco-folder.c:368
#19 0xb7db2779 in camel_folder_append_message (folder=0x821e5e0,
message=0x8277ef8, info=0x82b6948,
    appended_uid=0xb4104038, ex=0xb4ad732c) at camel-folder.c:665
#20 0xb7db3b7f in transfer_message_to (source=0x821e540, uid=0xb42d60d4
"9", dest=0x821e5e0,
    transferred_uid=0xb4104038, delete_original=1, ex=0xb4ad732c) at
camel-folder.c:1388
#21 0xb7db3ce0 in transfer_messages_to (source=0x821e540,
uids=0xb4102710, dest=0x821e5e0,
    transferred_uids=0xb4ad7328, delete_originals=1, ex=0xb4ad732c) at
camel-folder.c:1423
#22 0xb7db3f06 in camel_folder_transfer_messages_to (source=0x821e540,
uids=0xb4102710, dest=0x821e5e0,
    transferred_uids=0xb4ad7328, delete_originals=1, ex=0xb4ad732c) at
camel-folder.c:1474
#23 0xb7dfa770 in tny_camel_folder_transfer_msgs_default
(self=0x825b400, headers=0x82a20c0,
    folder_dst=0x81eb358, delete_originals=1, err=0xb4ad73f4) at
tny-camel-folder.c:1791
#24 0xb7dfa367 in tny_camel_folder_transfer_msgs (self=0x825b400,
headers=0x82a20c0, folder_dst=0x81eb358,
    delete_originals=1, err=0xb4ad73f4) at tny-camel-folder.c:1732
#25 0xb7b241c2 in tny_folder_transfer_msgs (self=0x825b400,
headers=0x82a20c0, folder_dst=0x81eb358,
    delete_originals=1, err=0xb4ad73f4) at tny-folder.c:536
#26 0xb7dfa01a in tny_camel_folder_transfer_msgs_async_thread
(thr_user_data=0x82746f0)
    at tny-camel-folder.c:1651