[oi-dev] [developer] [Samba] gencache.tdb: device busy

Sun Apr 21 12:12:17 UTC 2019

It's possible there's a bug.  It's also possible you're getting really
unlucky and the uninitialized mutex looks valid because the magic is valid.

On Sun, Apr 21, 2019, 06:10 Rouven WEILER <Rouven_Weiler at gmx.net> wrote:

> Dear all,
>
> trying to make samba work and getting rid of my error message
>
> [2019/04/01 09:51:41.112485,  0] ../../lib/tdb_wrap/tdb_wrap.c:64(tdb_wrap_log)
>  tdb(/var/samba/lock/gencache.tdb): tdb_open_ex: tdb_mutex_init failed for /var/samba/lock/gencache.tdb: Device busy
>
>
> I followed the info of Youzhong. It definitely works. So thankx.
> BUT: The OS (OpenIndiana; state of April,19th) is patched against the
> illumos issue 9959
>
> So there might be some mechanism (maybe MUTEX_MAGIC) that avoids the
> initialization of the mutex before init.
> I am really not deep in all that pthread stuff…
>
> Is there the possiblity that there is a bug in the code base of issue 9959?
>
>
> Best regards
>
> Rouven
>
>
> Am 18.04.2019 um 19:20 schrieb Robert Mustacchi <rm at joyent.com>:
>
> On 4/18/19 10:12 , Youzhong Yang wrote:
>
> Little bit confused. The page  https://www.openindiana.org/download/ shows
> latest ISO is dated 2018.10, but 9959 fix was submitted on 11/26/2018, I
> guess Hipster doesn't have it.
>
>
> The ISO is just the install image. Generally, after using that to
> bootstrap, then folks will update to latest bits via IPS. As a result,
> the ISO isn't updated (and generally doesn't have to be) quite as often.
>
> Robert
>
> On Thu, Apr 18, 2019 at 12:38 PM Rouven WEILER <Rouven_Weiler at gmx.net>
> wrote:
>
> On my system the issue is solved and the sources are patched accordingly.
> Thus, the issue seems to be somewhere else.
>
> Am 18.04.2019 um 18:27 schrieb Rouven WEILER <Rouven_Weiler at gmx.net>:
>
> concerning openindiana I am using the most recent one. I right now asked
> if the issue is solved in the latest version.
>
> another interesting thing is that older samba versions do not throw EBUSY,
> although on the same underlying system.
>
>
>
> Am 18.04.2019 um 18:07 schrieb Youzhong Yang <youzhong at gmail.com>:
>
> That is interesting. I am curious about how pthread_mutexattr_init ends up
> returning EBUSY. What verison of Openindiana are you running? is there a
> link pointing to the fix that it has for 9959?
>
> On Thu, Apr 18, 2019 at 11:53 AM Rouven WEILER <Rouven_Weiler at gmx.net>
> wrote:
>
> I understand and see that it works, but as written below
> pthread_mutexattr_init throws EBUSY, not pthread_mutex_init.
>
> Also Openindiana seems to include the patch for issue 9959 mentioned. I
> will clarify that to make sure.
>
> I just want to make sure that the patch you suggest aims for the issue
> and is not a workaround.
>
>
> Am 18.04.2019 um 16:09 schrieb Youzhong Yang <youzhong at gmail.com>:
>
> I reproduced the issue on a smartos version which does not have the fix
> for  https://www.illumos.org/issues/9959.
>
> The pthread_mutex_init() at line 590 returns EBUSY:
> ret = pthread_mutex_init(chain, &ma);
>
>
> https://git.samba.org/?p=samba.git;a=blob;f=lib/tdb/common/mutex.c;h=8a122d5d6a2ec321bce25cf06062acc808f1e126;hb=HEAD#l590
>
>
> Then I applied the following patch to lib/tdb/common/mutex.c:
>
> # git grep -B 1 -n pthread_mutex_init lib/tdb/common/mutex.c
> lib/tdb/common/mutex.c-590-             bzero(chain,
> sizeof(pthread_mutex_t));
> lib/tdb/common/mutex.c:591:             ret = pthread_mutex_init(chain,
> &ma);
> --
> lib/tdb/common/mutex.c-599-     bzero(&m->allrecord_mutex,
> sizeof(pthread_mutex_t));
> lib/tdb/common/mutex.c:600:     ret =
> pthread_mutex_init(&m->allrecord_mutex, &ma);
> --
> lib/tdb/common/mutex.c-693-     bzero(&m, sizeof(pthread_mutex_t));
> lib/tdb/common/mutex.c:694:     ret = pthread_mutex_init(&m, &ma);
> --
> lib/tdb/common/mutex.c-891-     bzero(ptr, sizeof(pthread_mutex_t));
> lib/tdb/common/mutex.c:892:     ret = pthread_mutex_init(ptr, &ma);
>
> It works like a charm. Fair enough?
>
> So again I recommend either of the following two:
> - apply 9959 fix to your OS image, or use a newer version which has 9959
> fix
> - bzero pthread_mutex_t struct before calling pthread_mutex_init().
>
> In my environment I applied bzero patch to all pthread_mutex_init() calls
> in the entire samba code base, you know, who knows what is going to happen.
>
>
>
> On Thu, Apr 18, 2019 at 4:29 AM Rouven WEILER <Rouven_Weiler at gmx.net>
> wrote:
>
> That sounds reasonable!
> Could you help me to dtrace that in a feasible way? Up to now I am not
> used to dtrace. Except knowing what is and that its powerful.
>
> Am 18.04.2019 um 09:29 schrieb Jason King <jason.brian.king at gmail.com>:
>
> It appears that the robust mutexes are mmapped from the .tdb file.
> EBUSY means that the mutex has already been intialized.  It also appears
> that if the TDB_CLEAR_IF_FIRST flag is _not_ set when opening the tdb, it
> will try to initialize the mutexes.  I’m wondering if the tdb file gets
> created, the memory image of the initialized mutexes is getting saved, then
> when it’s opened again, if that flag is not set, it tries to re-initialize
> the mutexes and fails (because they are already constructed) legitimately
> returning EBUSY.  If the samba code is in fact trying to reinitialize an
> already initialized mutex (dtrace might be able to help determine this — at
> this point it’s merely a supposition), that would explain the error.
>
>
>
>
> From: Rouven WEILER <rouven_weiler at gmx.net> <rouven_weiler at gmx.net>
> Reply: illumos-developer <developer at lists.illumos.org>
> <developer at lists.illumos.org>
> Date: April 18, 2019 at 12:48:48 AM
> To: Youzhong Yang <youzhong at gmail.com> <youzhong at gmail.com>
> Cc: Robert Mustacchi <rm at joyent.com> <rm at joyent.com>, Toomas Soome via
> illumos-developer <developer at lists.illumos.org>
> <developer at lists.illumos.org>
> Subject:  [developer] Aw: Re: [Samba] gencache.tdb: device busy
>
> You are totally right. That's the same I got from the man pages.
>
> The responsible code lines of samba also seems to bear no issue and also
> this issue arises on samba version 4.10.x not on earlier ones.
> In addition, there seems to be only a problem with
> illumos/openindiana...
> That's why I do not know how to get that fixed. Up to now I hadn't time
> to dtrace.
>
> Only thing I got so far: When the mutexattr is already set the return
> value will result on undefined behaviour.
> But why only after version 4.10.x on openindiana/illumos?
>
> Just for completion here the codelines of samba:
>
> https://git.samba.org/?p=samba.git;a=blob;f=lib/tdb/common/mutex.c;h=8a122d5d6a2ec321bce25cf06062acc808f1e126;hb=HEAD#l570
>
>
>
> Gesendet: Mittwoch, 17. April 2019 um 19:19 Uhr
> Von: "Youzhong Yang" <youzhong at gmail.com>
> An: "Rouven WEILER" <Rouven_Weiler at gmx.net>
> Cc: "Robert Mustacchi" <rm at joyent.com>, "Toomas Soome via
> illumos-developer" <developer at lists.illumos.org>
> Betreff: Re: [Samba] gencache.tdb: device busy
>
> Unless I am totally wrong, pthread_mutexattr_init() shouldn't return
> EBUSY:
>
>
> http://src.illumos.org/source/xref/illumos-gate/usr/src/lib/libc/port/threads/pthr_mutex.c#37
>
>
> On Tue, Apr 16, 2019 at 2:45 PM Rouven WEILER <Rouven_Weiler at gmx.net[
> mailto:Rouven_Weiler at gmx.net <Rouven_Weiler at gmx.net>]> wrote:Hi Robert
> & Youzhong,
>
> I got a response from the Samba-Devs.
> Would the issue mentioned by Youzhong also hot pthread_mutexattr_t?
>
> Concerning dtrace I hadn’t the time yet but I will check for that.
> Is there maybe a way to trace all forks of smbd? Usually the issue
> arises after the fork…
>
> FIND BELOW THE STATEMENT FROM samba.org[http://samba.org]:
>
> This doesn't look exactly the same. In your
> log below you say:
>
> ret = pthread_mutexattr_init(&ma); in line 570
> I got errorno 16 --> device busy.
>
> But the bug report is about needing the value
> passed to pthread_mutex_init() needing to be
> zero, not the value passed to pthread_mutexattr_init().
>
> Can you just try adding '= {0}' to all the
> places where we declare:
>
> pthread_mutexattr_t ma
>
> (i.e. make it say)
>
> pthread_mutexattr_t ma = {0};
>
> and see if it makes your problem go away ?
>
> END OF STATEMENT
>
>
> Anfang der weitergeleiteten Nachricht:
>
> Von: Jeremy Allison via samba <samba at lists.samba.org[
>
> mailto:samba at lists.samba.org <samba at lists.samba.org>]>
>
> Betreff: Aw: [Samba] gencache.tdb: device busy
> Datum: 16. April 2019 um 02:07:05 MESZ
> An: Rouven WEILER <Rouven_Weiler at gmx.net[mailto:Rouven_Weiler at gmx.net
>
> <Rouven_Weiler at gmx.net>]>
>
> Kopie: samba at lists.samba.org[mailto:samba at lists.samba.org
>
> <samba at lists.samba.org>]
>
> Antwort an: Jeremy Allison <jra at samba.org[mailto:jra at samba.org
>
> <jra at samba.org>]>
>
>
> On Fri, Apr 12, 2019 at 09:46:04AM +0200, Rouven WEILER via samba
>
> wrote:
>
>
>
> Hi Jeremy,
>
> I got some info on that topic from the illumos devs:
>
>
> It's a sporadic issue, you're lucky enough to not encounter it on
>
> 4.9.5.
>
>
> I confirmed in 4.10.2, it happens:
>
> winbindd.log:  tdb(/tmw-nas-3p/samba/var/lock/gencache.tdb):
>
> tdb_open_ex: tdb_mutex_init failed for
> /tmw-nas-3p/samba/var/lock/gencache.tdb: Device busy
>
>
> So either apply OS fix, or apply a software fix (zeroing
>
> pthread_mutex_t before pthread_mutex_init()).
>
>
> This all should be based on the following issue:
>
>
> https://www.illumos.org/issues/9959[https://www.illumos.org/issues/9959]
>
>
> As far as I understand the issue making an software fix in samba for
>
> the OS seems more reasonable since the problem can occur sporadic and thus
> again...
>
> Could you tell me how to help to fix that bug?
>
>
> This doesn't look exactly the same. In your
> log below you say:
>
> ret = pthread_mutexattr_init(&ma); in line 570
> I got errorno 16 --> device busy.
>
> But the bug report is about needing the value
> passed to pthread_mutex_init() needing to be
> zero, not the value passed to pthread_mutexattr_init().
>
> Can you just try adding '= {0}' to all the
> places where we declare:
>
> pthread_mutexattr_t ma
>
> (i.e. make it say)
>
> pthread_mutexattr_t ma = {0};
>
> and see if it makes your problem go away ?
>
>
> Gesendet: Dienstag, 02. April 2019 um 18:59 Uhr
> Von: "Jeremy Allison" <jra at samba.org[mailto:jra at samba.org
>
> <jra at samba.org>]>
>
> An: "Rouven WEILER" <Rouven_Weiler at gmx.net[
>
> mailto:Rouven_Weiler at gmx.net <Rouven_Weiler at gmx.net>]>
>
> Cc: samba at lists.samba.org[mailto:samba at lists.samba.org
>
> <samba at lists.samba.org>]
>
> Betreff: Re: Re: [Samba] gencache.tdb: device busy
> On Tue, Apr 02, 2019 at 01:24:19PM +0200, Rouven WEILER wrote:
>
>
>
> I added LOG statements to mutex.c printing the strerror from the
>
> return values.
>
>
> From
>
> ret = pthread_mutexattr_init(&ma); in line 570
>
> I got errorno 16 --> device busy.
>
> But due the manual of pthread_mutex_attr_init() there should only be
>
> ENOMEM and EINVAL...
>
>
> Doing gdb smbd -> run
> Doe not reveal anything, but I never used gdb for debugging
>
> anything. I just gave it a shot...
>
>
> Sorry, looks a little like the libc/pthread_mutex support
> on Solaris is broken. You might want to raise this on a
> Solaris/Illumos forum.
>
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