Middleman stuck

middleman-strace.log

[…]
clock_gettime(CLOCK_MONOTONIC, {6550, 552084825}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6552, 554244104}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6554, 556443293}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6556, 558659345}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6558, 560845425}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6560, 563071810}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6562, 564191861}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6564, 566401804}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = 0 (Timeout)
clock_gettime(CLOCK_MONOTONIC, {6566, 568559731}) = 0
select(12, [10 11], NULL, NULL, {2, 0}) = ? ERESTARTNOHAND (To be restarted if no handler)