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Call for pthread_join() does not set errno value even though return values
looks like that. For now assign errno from return value and still use
strerror() to print some error message as this seems to be commonly used.
Add also log_sys_error() message for error close of local pipe.
We need to be sure that /var/run and /var/lock is always there.
(E.g. these two directories could be using tmpfs which then loose
all the content after reboot.)
Detect existence of new SELinux selabel interface during configure.
Use new dm_prepare_selinux_context instead of dm_set_selinux_context.
We should set the SELinux context before the actual file system object creation.
The new dm_prepare_selinux_context function sets this using the selabel_lookup
fn in conjuction with the setfscreatecon fn. If selinux/label.h interface
(that should be a part of the selinux library) is not found during configure,
we fallback to the original matchpathcon function instead.
The management threads (main_loop, the socket thread) could close a single fd
twice in a row sometimes. At least one other thread can be running at the same
time as the threads doing the double close. That one running thread also
happens to do some IO (namely, open /proc/devices, read from it, close it). If
there was enough "demand" for the local socket, this could happen:
- a connection to clvmd is about to finish, let's say the fd is 13 (it often
happens to be in my test script, don't ask why)
- the local_sock thread calls close(13)
- the lvm thread calls open("/proc/devices"...) and gets 13
- the main_loop thread calls close(13) [OOPS!]
- new connection arrives, and is accept'd by a (new) local_sock thread
- the accept gives an fd of 13 (since it's the lowest free fd at this point)
- the lvm thread gets around to read from it's /proc/devices handle... 13,
again
- the lvm thread hangs forever trying to read from the socket instead of
/proc/devices
Signed-off-by: Petr Rockai <prockai@redhat.com>
Reviewed-by: Milan Broz <mbroz@redhat.com>
It's quite new feature which is not supported by older compilers.
So until some better macros are introduced into LVM code - hotfix current
compilation problems and compile this code only for __clang__ defining compilers.
The signalling code (pthread_cond_signal/pthread_cond_wait) in the
pre_and_post_thread was using the wait mutex (see man pthread_cond_wait)
incorrectly, and this could cause clvmd to deadlock when timing was
right. Detailed explanation of the problem follows.
There is a single mutex around (L for Lock, U for Unlock), a signal (S) and a
wait (W). C for pthread_create. Time flows from left to right, each arrow is a
thread.
So first the "naive" scenario, with no mutex (PPT = pre_and_post_thread, MCT =
main clvmd thread; well actually the thread that does read_from_local_sock). I
will also use X, for a moment when MCT actually waits for something to happen
that PPT was supposed to do.
MCT -----C ------S--X-----S----X----------------------S------XXXXXXXXX
| everything OK up to this --> <-- point...
PPT -----WWW-----WWWW------------------------------WWWWWWWWWWWWW
Ok, so pthread API actually does not let you use W/S like that. It goes out of
its way to tell you that you need a mutex to protect the W so that the above
cannot happen. *But* if you are creative and just lock around the W's and S's,
this happens:
MCT ----C-----LSU----X-----LSU----X------------LSU------XXXXXXX
|
PPT ---LWWWU-------LWWWWU-----------------------LWWWWWWWWW
Ooops. Nothing changed (the above is what actually was done by clvmd before
this satch). So let's do it differently, holding L locked *all* the time in
PPT, unless we are actually in W (this is something that the pthread API does
itself, see the man page).
MCT ----C-----LSU------X---LSU---X-----LLLLLLLSU----X----
| (and they live happily ever after)
PPT L---WWWWW---------WWWW----------------W----------
So W actually ensures that L is unlocked *atomically* together with entering
the wait. That means that unless PPT is actually waiting, it cannot be
signalled by MCT. So if MCT happens to signal it too soon (it wasn't waiting
yet), it (MCT) will be blocked on the mutex (L), until PPT is actually ready to
do something.
Switch dmeventd to use dm_create_lockfile and drop duplicate code.
Allow clvmd pidfile to be configurable.
Switch cmirrord and clvmd to use dm_create_lockfile.
interface it should be using, it can still be overriden with -I.
If corosync isn't running or there is no information then the usual
checking will happen.
This code only builds if corosync is available.
Current code, when need to ensure that volume is not
active on remote node, it need to try to exclusive
activate volume.
Patch adds simple clvmd command which queries all nodes
for lock for given resource.
The lock type is returned in reply in text.
(But code currently uses CR and EX modes only.)
