InnoDB: Warning: a long semaphore wait: --Thread 1470490944 has waited at btr/btr0cur.c line 1501 for 241.00 seconds the semaphore: X-lock on RW-latch at 0x2aaaaeccb0b8 created in file btr/btr0sea.c line 139 a writer (thread id 1470490944) has reserved it in mode wait exclusive number of readers 1, waiters flag 1 Last time read locked in file row/row0sel.c line 3499 Last time write locked in file btr/btr0sea.c line 516 InnoDB: Warning: a long semaphore wait: --Thread 1266551104 has waited at btr/btr0cur.c line 2343 for 241.00 seconds the semaphore: X-lock on RW-latch at 0x2aaaaeccb0b8 created in file btr/btr0sea.c line 139 a writer (thread id 1470490944) has reserved it in mode wait exclusive number of readers 1, waiters flag 1 Last time read locked in file row/row0sel.c line 3499 Last time write locked in file btr/btr0sea.c line 516 InnoDB: Warning: a long semaphore wait: --Thread 1438542144 has waited at row/row0mysql.c line 1740 for 241.00 seconds the semaphore: S-lock on RW-latch at 0xcfe300 created in file dict/dict0dict.c line 725 a writer (thread id 1204250944) has reserved it in mode exclusive number of readers 0, waiters flag 1 Last time read locked in file row/row0mysql.c line 1740 Last time write locked in file row/row0mysql.c line 1775 ... ===================================== 110225 9:38:18 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 52 seconds ---------- SEMAPHORES ---------- OS WAIT ARRAY INFO: reservation count 29397677, signal count 26596803 --Thread 1470490944 has waited at btr/btr0cur.c line 1501 for 256.00 seconds the semaphore: X-lock on RW-latch at 0x2aaaaeccb0b8 created in file btr/btr0sea.c line 139 a writer (thread id 1470490944) has reserved it in mode wait exclusive number of readers 1, waiters flag 1 Last time read locked in file row/row0sel.c line 3499 Last time write locked in file btr/btr0sea.c line 516 --Thread 1266551104 has waited at btr/btr0cur.c line 2343 for 256.00 seconds the semaphore: X-lock on RW-latch at 0x2aaaaeccb0b8 created in file btr/btr0sea.c line 139 a writer (thread id 1470490944) has reserved it in mode wait exclusive number of readers 1, waiters flag 1 Last time read locked in file row/row0sel.c line 3499 Last time write locked in file btr/btr0sea.c line 516 ... ---TRANSACTION 20 2789018714, ACTIVE 256 sec, process no 31708, OS thread id 1470490944 updating or deleting, thread declared inside InnoDB 499 mysql tables in use 1, locked 1 2 lock struct(s), heap size 368, 1 row lock(s), undo log entries 1 MySQL thread id 78575520, query id 2790900029 mag-rob38.osl.basefarm.net 79.171.81.218 root Updating UPDATE source SET robot_cluster = '7' WHERE sourceid = '107201' (It seems that thread 1470490944 is waiting for itself)