background job stops with "Can't obtain shared reading index lock"

[hoschmieder]

Environment:
CentOS 7.1
Owncloud 8.1 (latest) from OC-Repro
about 30 User, about 100GB Files
When i am running (as apache) "php /var/www/html/owncloud/cron.php" i get the following error:

{"reqId":"JICzl\/JsqrfXXg9xbPy7","remoteAddr":"","app":"PHP","message":"Undefined index: REQUEST_URI at \/var\/www\/html\/owncloud\/apps\/contacts\/appinfo\/app.php#35","level":3,"time":"2015-08-02T14:41:30+00:00"}
{"reqId":"JICzl\/JsqrfXXg9xbPy7","remoteAddr":"","app":"PHP","message":"Undefined index: REQUEST_URI at \/var\/www\/html\/owncloud\/apps\/documents\/appinfo\/app.php#49","level":3,"time":"2015-08-02T14:41:30+00:00"}
{"reqId":"JICzl\/JsqrfXXg9xbPy7","remoteAddr":"","app":"no app in context","message":"Error while running background job: Can't obtain shared reading index lock","level":3,"time":"2015-08-02T14:41:31+00:00"}
{"reqId":"JICzl\/JsqrfXXg9xbPy7","remoteAddr":"","app":"no app in context","message":"Error while running background job: Can't obtain shared reading index lock","level":3,"time":"2015-08-02T14:41:31+00:00"}

I did now an strace on that job and saw that the indexer tries to find a file in folder of user1 wich is not there. That file is shared from user2 with user1.
Then the indexer moves to the folder of user2 and tries:
access("/daten/office/lucene_index/v0.6.0", F_OK) = -1 ENOENT (No such file or directory)
wich not exist. What happens after that i could not understand: it tries to delete the index-directory:

access("/daten/office/lucene_index/v0.6.0", F_OK) = -1 ENOENT (No such file or directory)
brk(0)                                  = 0x7faf72c71000
brk(0x7faf72cb1000)                     = 0x7faf72cb1000
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\376\0\0\0\3SELECT `fileid`, `storage`,"..., 258) = 258
read(3, "\1\0\0\1\rB\0\0\2\3def\10owncloud\foc_fileca"..., 16384) = 1043
access("/daten/office/lucene_index", F_OK) = 0
stat("/daten/office/lucene_index", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
access("/daten/office/.", W_OK)         = 0
access("/daten/office/lucene_index", W_OK) = 0
openat(AT_FDCWD, "/daten/office/lucene_index", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 4
getdents(4, /* 2 entries */, 32768)     = 48
lseek(4, 0, SEEK_SET)                   = 0
getdents(4, /* 2 entries */, 32768)     = 48
getdents(4, /* 0 entries */, 32768)     = 0
rmdir("/daten/office/lucene_index")     = 0
close(4)                                = 0
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\376\0\0\0\3SELECT `fileid`, `storage`,"..., 258) = 258
read(3, "\1\0\0\1\rB\0\0\2\3def\10owncloud\foc_fileca"..., 16384) = 1043
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "4\0\0\0\3DELETE FROM `oc_filecache` "..., 56) = 56
read(3, "\7\0\0\1\0\1\0\2\0\0\0", 16384) = 11
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\342\0\0\0\3SELECT `fileid`, `storage`,"..., 230) = 230
read(3, "\1\0\0\1\rB\0\0\2\3def\10owncloud\foc_fileca"..., 16384) = 955
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "4\0\0\0\3DELETE FROM `oc_filecache` "..., 56) = 56
read(3, "\7\0\0\1\0\0\0\2\0\0\0", 16384) = 11
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "o\0\0\0\3SELECT `fileid` FROM `oc_fi"..., 115) = 115
read(3, "\1\0\0\1\1B\0\0\2\3def\10owncloud\foc_fileca"..., 16384) = 100
stat("/daten/office/.", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\250\0\0\0\3UPDATE `oc_filecache` SET `"..., 172) = 172
read(3, "0\0\0\1\0\0\0\2\0\0\0(Rows matched: 0  Cha"..., 16384) = 52
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\376\0\0\0\3SELECT `fileid`, `storage`,"..., 258) = 258
read(3, "\1\0\0\1\rB\0\0\2\3def\10owncloud\foc_fileca"..., 16384) = 1018
stat("/daten/", {st_mode=S_IFDIR|0770, st_size=4096, ...}) = 0
nanosleep({0, 1000}, NULL)              = 0
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\235\0\0\0\3UPDATE `oc_filecache` SET `"..., 161) = 161
read(3, "0\0\0\1\0\1\0\2\0\0\0(Rows matched: 1  Cha"..., 16384) = 52
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\376\0\0\0\3SELECT `fileid`, `storage`,"..., 258) = 258
read(3, "\1\0\0\1\rB\0\0\2\3def\10owncloud\foc_fileca"..., 16384) = 1026
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\376\0\0\0\3SELECT `fileid`, `storage`,"..., 258) = 258
read(3, "\1\0\0\1\rB\0\0\2\3def\10owncloud\foc_fileca"..., 16384) = 1036
stat("/daten/office/", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
nanosleep({0, 1000}, NULL)              = 0
poll([{fd=3, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
write(3, "\234\0\0\0\3UPDATE `oc_filecache` SET `"..., 160) = 160
read(3, "0\0\0\1\0\1\0\2\0\0\0(Rows matched: 1  Cha"..., 16384) = 52
stat("/daten/office/lucene_index", 0x7ffd8f475db0) = -1 ENOENT (No such file or directory)

Is there a problem with shared files?
Or Is there something wrong within my installation?

Thanks for an idea.
Holger

[karlitschek]

@butonic can you have a look?

[SpeicherBox]

Do you have the encryption app enabled?