Fork imap process

[jrse]

When forking the imapprocess with active rbox_storage plugin,
the child process will wait forever for a mutex:

Stacktrace:

(gdb) bt
#0 0x00007f13661920cf in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0

#1 0x00007f1361379ace in Cond::Wait(Mutex&) () from /usr/lib64/librados.so.2

#2 0x00007f13613814eb in librados::RadosClient::watch_flush() () from /usr/lib64/librados.so.2

#3 0x00007f1361381753 in librados::RadosClient::shutdown() () from /usr/lib64/librados.so.2

#4 0x00007f1361336a58 in librados::Rados::shutdown() () from /usr/lib64/librados.so.2

#5 0x00007f1367948129 in __run_exit_handlers () from /lib64/libc.so.6

#6 0x00007f1367948175 in exit () from /lib64/libc.so.6

#7 0x00007f1363c32c5b in dg_resize_helper () from /opt/app/dovecot/lib/dovecot/libfundovecotgraphics.so.7

#8 0x00007f1363c32e2f in dovecot_graphics_resize_image_blob () from /opt/app/dovecot/lib/dovecot/libfundovecotgraphics.so.7

#9 0x00007f1364042bda in parse_message_part () from /opt/app/dovecot/lib/dovecot/lib91_fun_extended_listview_plugin.so

#10 0x00007f1364041a1e in parse_message_part () from /opt/app/dovecot/lib/dovecot/lib91_fun_extended_listview_plugin.so

#11 0x00007f136404367a in elv_save_mail_message_real () from /opt/app/dovecot/lib/dovecot/lib91_fun_extended_listview_plugin.so

#12 0x00007f13640438fd in elv_save_mail_message_by_guid () from /opt/app/dovecot/lib/dovecot/lib91_fun_extended_listview_plugin.so

#13 0x00007f1364043dda in elv_mail_transaction_commit () from /opt/app/dovecot/lib/dovecot/lib91_fun_extended_listview_plugin.so

#14 0x00007f1365d6b718 in notify_contexts_mail_transaction_commit () from /opt/app/dovecot/lib/dovecot/lib15_notify_plugin.so

#15 0x00007f1365d6c3b1 in notify_transaction_commit () from /opt/app/dovecot/lib/dovecot/lib15_notify_plugin.so

#16 0x00007f1365f7c354 in quota_mailbox_transaction_commit () from /opt/app/dovecot/lib/dovecot/lib10_quota_plugin.so

#17 0x00007f1367ff7171 in mailbox_transaction_commit_get_changes () from /opt/app/dovecot/lib/dovecot/libdovecot-storage.so.0

#18 0x00007f13682e68bc in mail_deliver_save () from /opt/app/dovecot/lib/dovecot/libdovecot-lda.so.0

#19 0x00007f13682e6c73 in mail_deliver () from /opt/app/dovecot/lib/dovecot/libdovecot-lda.so.0

#20 0x00005628c1429544 in client_input_data_write ()

#21 0x00005628c1429c93 in client_input_data_handle ()

#22 0x00005628c142bd8e in cmd_data ()

#23 0x00005628c14283bb in client_input_handle ()

#24 0x00007f1367d463fc in io_loop_call_io () from /opt/app/dovecot/lib/dovecot/libdovecot.so.0

#25 0x00007f1367d47707 in io_loop_handler_run_internal () from /opt/app/dovecot/lib/dovecot/libdovecot.so.0

#26 0x00007f1367d46485 in io_loop_handler_run () from /opt/app/dovecot/lib/dovecot/libdovecot.so.0

#27 0x00007f1367d46638 in io_loop_run () from /opt/app/dovecot/lib/dovecot/libdovecot.so.0

#28 0x00007f1367ce4113 in master_service_run () from /opt/app/dovecot/lib/dovecot/libdovecot.so.0

#29 0x00005628c14279f5 in main ()

[jrse]

Ansi C++ Standard:

§ 18.3/8The function exit() has additional behavior in this International Standard:— First, objects with static storage duration are destroyed and functions registered by calling atexit are

called. Non-local objects with static storage duration are destroyed in the reverse order of the completion

of their constructor. (Automatic objects are not destroyed as a result of calling exit().) ...

=> ~librados::Rados() is called due to the fact that librmb::RadosClient creates a static reference of librados::Rados on the stack this leads to the call of ~librados::Rados() ->shutdown();

There are two possible solutions for this problem:

1. Do not create librados::Rados on the stack
2. register additional exit handler with atexit and call _exit(0) if current process is the child process, within the exit handler to avoid additional calls to exit handlers.

[jrse]

we decided to implement solution number 2.

[jrse]

after discussing this issue again, we decided to implement solution 1, because solution two is more or less a workaround.