MariaDB becomes unresponsive and often crashes

2019-03-31 13:33:24 140115816994560 [Warning] InnoDB: A long semaphore wait:

--Thread 140353328404224 has waited at ha_innodb.cc line 15332 for 241.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140355166058240 has waited at ha_innodb.cc line 16119 for 232.00 seconds the semaphore:

Mutex at 0x56150b6aa040, Mutex SRV_MONITOR_FILE created srv0start.cc:1726, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140344273450752 has waited at dict0dict.cc line 1161 for 39.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140349093312256 has waited at dict0dict.cc line 1161 for 34.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140343849826048 has waited at ha_innodb.cc line 16119 for 203.00 seconds the semaphore:

Mutex at 0x56150b6aa040, Mutex SRV_MONITOR_FILE created srv0start.cc:1726, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140344697378560 has waited at dict0dict.cc line 1161 for 97.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140348086073088 has waited at dict0dict.cc line 1161 for 108.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140351210829568 has waited at dict0dict.cc line 1161 for 113.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140352057472768 has waited at dict0dict.cc line 1161 for 218.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140337616541440 has waited at dict0dict.cc line 1161 for 69.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140339030267648 has waited at row0ins.cc line 1938 for 130.00 seconds the semaphore:

S-lock on RW-latch at 0x7f70e33ba500 created in file dict0dict.cc line 1108

a writer (thread id 140115800209152) has reserved it in mode  exclusive

number of readers 0, waiters flag 1, lock_word: 0

Last time read locked in file row0ins.cc line 1938

Last time write locked in file dict0stats.cc line 2454

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140343283046144 has waited at dict0dict.cc line 1161 for 34.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2

2019-03-31 13:33:24 140115816994560 [Note] InnoDB: A semaphore wait:

--Thread 140344977544960 has waited at dict0dict.cc line 1161 for 139.00 seconds the semaphore:

Mutex at 0x7fa77a9f06c0, Mutex DICT_SYS created dict0dict.cc:1097, lock var 2