Yeah, that's what I see in the strace log.

I think that the problem/symptom is that the poll just times out and doesn't get data on the event-fd.

tail of indicator-datetime-service.strace.log:
11:00:28 eventfd2(0, O_NONBLOCK|O_CLOEXEC) = 22
11:00:28 write(22, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:28 write(6, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:28 futex(0xb580af10, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:28 futex(0xb580ab08, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:28 clock_gettime(CLOCK_MONOTONIC, {2931, 622027924}) = 0
11:00:28 futex(0xb5802f80, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:28 clock_gettime(CLOCK_MONOTONIC, {2931, 622178855}) = 0
11:00:28 poll([{fd=22, events=POLLIN}], 1, 180000) = 1 ([{fd=22, revents=POLLIN}])
11:00:28 clock_gettime(CLOCK_MONOTONIC, {2931, 622230836}) = 0
11:00:28 clock_gettime(CLOCK_MONOTONIC, {2931, 622254879}) = 0
11:00:28 poll([{fd=22, events=POLLIN}], 1, 180000) = 1 ([{fd=22, revents=POLLIN}])
11:00:28 read(22, "\1\0\0\0\0\0\0\0", 16) = 8
11:00:28 clock_gettime(CLOCK_MONOTONIC, {2931, 622328380}) = 0
11:00:28 clock_gettime(CLOCK_MONOTONIC, {2931, 622352161}) = 0
11:00:28 poll([{fd=22, events=POLLIN}], 1, 180000 <detached ...>

and here just happens nothing, except a timeout after 180000 miliseconds (3 minutes). My guess is that there should have been a return with read action on fd=22. Similar as earlier:

11:00:25 eventfd2(0, O_NONBLOCK|O_CLOEXEC) = 8
11:00:25 write(8, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:25 write(6, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:25 futex(0xb580af10, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 futex(0xb580ab08, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 426833813}) = 0
11:00:25 futex(0xb5802f80, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 poll([{fd=8, events=POLLIN}], 1, 0) = 1 ([{fd=8, revents=POLLIN}])
11:00:25 write(6, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:25 futex(0xb580af10, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 futex(0xb580ab08, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 427817851}) = 0
11:00:25 futex(0xb5802f80, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 poll([{fd=8, events=POLLIN}], 1, 0) = 1 ([{fd=8, revents=POLLIN}])
11:00:25 read(8, "\3\0\0\0\0\0\0\0", 16) = 8
11:00:25 poll([{fd=8, events=POLLIN}], 1, 0) = 0 (Timeout)
11:00:25 read(8, 0xbfa5694c, 16)        = -1 EAGAIN (Resource temporarily unavailable)
11:00:25 write(8, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:25 close(8)                       = 0
11:00:25 eventfd2(0, O_NONBLOCK|O_CLOEXEC) = 8
11:00:25 write(8, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:25 write(6, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:25 futex(0xb580af10, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 futex(0xb580ab08, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 429068530}) = 0
11:00:25 futex(0xb5802f80, FUTEX_WAKE_PRIVATE, 1) = 1
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 429726382}) = 0
11:00:25 poll([{fd=8, events=POLLIN}], 1, 25000) = 1 ([{fd=8, revents=POLLIN}])
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 429874461}) = 0
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 429945589}) = 0
11:00:25 poll([{fd=8, events=POLLIN}], 1, 25000) = 1 ([{fd=8, revents=POLLIN}])
11:00:25 read(8, "\1\0\0\0\0\0\0\0", 16) = 8
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 430235853}) = 0
11:00:25 clock_gettime(CLOCK_MONOTONIC, {2928, 430307703}) = 0
11:00:25 poll([{fd=8, events=POLLIN}], 1, 24999) = 1 ([{fd=8, revents=POLLIN}])
11:00:25 read(8, "\1\0\0\0\0\0\0\0", 16) = 8
11:00:25 write(8, "\1\0\0\0\0\0\0\0", 8) = 8
11:00:25 close(8)                       = 0
11:00:25 gettimeofday({1395223225, 139383}, NULL) = 0
11:00:25 write(6, "\1\0\0\0\0\0\0\0", 8) = 8


I've no idea what this eventfd is, but I guess that is the pointer to the problem.