Description:
error log head
detail in file
InnoDB: Warning: a long semaphore wait:
--Thread 139737025918720 has waited at ../../../storage/innobase/buf/buf0buf.c line 1181 for 4906.00 seconds the semaphore:
Mutex at 0x7f175dbfdcb8 created file ../../../storage/innobase/buf/buf0buf.c line 600, lock var 0
waiters flag 0
InnoDB: ###### Starts InnoDB Monitor for 30 secs to print diagnostic info:
InnoDB: Pending preads 0, pwrites 0
=====================================
181107 19:22:29 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 11 seconds
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 17535445, signal count 17383270
--Thread 139736956786432 has waited at ../../../storage/innobase/include/btr0btr.ic line 28 for 11.00 seconds the semaphore:
S-lock on RW-latch at 0x7f1715e68470 created in file ../../../storage/innobase/buf/buf0buf.c line 550
a writer (thread id 139736956786432) has reserved it in mode exclusive
number of readers 0, waiters flag 1
Last time read locked in file ../../../storage/innobase/btr/btr0pcur.c line 249
Last time write locked in file ../../../storage/innobase/buf/buf0buf.c line 1823
Mutex spin waits 0, rounds 131168198, OS waits 1842101
RW-shared spins 32601543, OS waits 15333516; RW-excl spins 119646, OS waits 40381
How to repeat:
can not repeat
Suggested fix:
I guess some thing in buf reqire a lock holed by io operations.
and io read is too busy to release the lock
