# SEMAPHORES - waiting on an RW-latch created\_ in btr0sea.c **URL:** \ **Category:** Percona Server for MySQL 5.6\ **Created:** [April 9, 2019, 5:20am UTC](https://forums.percona.com/t/semaphores-waiting-on-an-rw-latch-created-in-btr0sea-c/6956 "2019-04-09T05:20:10Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![pooja.gupta](https://avatars.discourse-cdn.com/v4/letter/p/258eb7/32.png) [@pooja.gupta](https://forums.percona.com/u/pooja.gupta)\ **Post date:** [April 9, 2019, 5:20am UTC](https://forums.percona.com/t/semaphores-waiting-on-an-rw-latch-created-in-btr0sea-c/6956/1 "2019-04-09T05:20:10Z")
Can see lots of latches in the error log. Its increasing load on the server, high CPU utilization and High I/O. Mysql version is - 5.6.39-83.1 Error log - * * * ## SEMAPHORES OS WAIT ARRAY INFO: reservation count 202249793 –Thread 139909786564352 has waited at btr0pcur.cc line 467 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x7f41132df320 ‘&block-\>lock’ a writer (thread id 139909862520576) has reserved it in mode wait exclusive number of readers 1, waiters flag 1, lock\_word: ffffffffffffffff Last time read locked in file row0sel.cc line 3346 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/row/row0row.cc line 823 –Thread 139909795370752 has waited at btr0sea.cc line 954 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x23d9658 ‘&btr\_search\_latch\_arr[i]’ number of readers 3, waiters flag 0, lock\_word: ffffd Last time read locked in file btr0sea.cc line 954 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/btr/btr0sea.cc line 705 –Thread 139909849413376 has waited at row0sel.cc line 3346 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x7f41132df320 ‘&block-\>lock’ a writer (thread id 139909862520576) has reserved it in mode wait exclusive number of readers 1, waiters flag 1, lock\_word: ffffffffffffffff Last time read locked in file row0sel.cc line 3346 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/row/row0row.cc line 823 –Thread 139909862520576 has waited at row0row.cc line 823 for 0.0000 seconds the semaphore: X-lock (wait\_ex) on RW-latch at 0x7f41132df320 ‘&block-\>lock’ a writer (thread id 139909862520576) has reserved it in mode wait exclusive number of readers 1, waiters flag 1, lock\_word: ffffffffffffffff Last time read locked in file row0sel.cc line 3346 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/row/row0row.cc line 823 –Thread 139909900818176 has waited at btr0cur.cc line 3786 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x7f41132df320 ‘&block-\>lock’ a writer (thread id 139909862520576) has reserved it in mode wait exclusive number of readers 1, waiters flag 1, lock\_word: ffffffffffffffff Last time read locked in file row0sel.cc line 3346 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/row/row0row.cc line 823 –Thread 139909836089088 has waited at row0sel.cc line 3346 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x7f406d31ed20 ‘&block-\>lock’ number of readers 1, waiters flag 0, lock\_word: fffff Last time read locked in file row0sel.cc line 3346 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/row/row0ins.cc line 2718 –Thread 139909349865216 has waited at btr0sea.cc line 1380 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x23d9658 ‘&btr\_search\_latch\_arr[i]’ number of readers 2, waiters flag 0, lock\_word: ffffe Last time read locked in file btr0sea.cc line 954 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/btr/btr0sea.cc line 705 –Thread 139909854123776 has waited at buf0buf.cc line 3303 for 0.0000 seconds the semaphore: Mutex at 0x7f40a4ad8840 ‘&block-\>mutex’, lock var 0 waiters flag 0 –Thread 139909777962752 has waited at btr0sea.cc line 1380 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x23d9658 ‘&btr\_search\_latch\_arr[i]’ number of readers 4, waiters flag 0, lock\_word: ffffc Last time read locked in file btr0sea.cc line 954 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/btr/btr0sea.cc line 705 –Thread 139909864568576 has waited at btr0sea.cc line 1380 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x23d9658 ‘&btr\_search\_latch\_arr[i]’ number of readers 3, waiters flag 0, lock\_word: ffffd Last time read locked in file btr0sea.cc line 954 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/btr/btr0sea.cc line 705 –Thread 139909845509888 has waited at btr0pcur.cc line 467 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x7f41132df320 ‘&block-\>lock’ a writer (thread id 139909862520576) has reserved it in mode wait exclusive number of readers 1, waiters flag 1, lock\_word: ffffffffffffffff Last time read locked in file row0sel.cc line 3346 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/row/row0row.cc line 823 –Thread 139909875422976 has waited at btr0sea.cc line 1380 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x23d9658 ‘&btr\_search\_latch\_arr[i]’ number of readers 2, waiters flag 0, lock\_word: ffffe Last time read locked in file btr0sea.cc line 954 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/btr/btr0sea.cc line 705 –Thread 139909325494016 has waited at btr0sea.cc line 705 for 0.0000 seconds the semaphore: X-lock on RW-latch at 0x23d9658 ‘&btr\_search\_latch\_arr[i]’ number of readers 2, waiters flag 0, lock\_word: ffffe Last time read locked in file btr0sea.cc line 954 Last time write locked in file /mnt/workspace/percona-server-5.6-redhat-binary/label\_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.39-83.1/storage/innobase/btr/btr0sea.cc line 705 –Thread 139909864158976 has waited at btr0pcur.cc line 467 for 0.0000 seconds the semaphore: S-lock on RW-latch at 0x7f41132df320 ‘&block-\>lock’ a writer (thread id 139909862520576) has reserved it in mode wait exclusive number of readers 1, waiters flag 1, lock\_word: ffffffffffffffff Last time read locked in file row0sel.cc line 3346