>Description:
On several occasions I reported problems with MySQL and our Webmail installation
(using the program IMP). All MySQL processes would lock. No process would be
shown to execute. The Only thing to correct the problem was to kill MySQL and
restart Apache.
People at MySQL pointed at a faulty lpthread library, but having no access to
the latest SGI bug list, I could not verify. I try several things as
- use --skip-locking
- use low-priority-thread
- don't use persistent connections in php.ini
- etc...
Lockups continued.
This was back in december.
Later at the beginning of the year, I decided to try the new versions with
the test suite. I tried on different SGI boxes we have here. Not one could
complete the tests. They would all lock at one point or another, waiting for
a signal.
Recently, I decided to test with a different user than root. I reported the
results in february (re: lockup in test suite on SGI). All tests worked without
problem on all servers tried.
It has now been more than a week without any lockup in our production webmail
environment. I upgraded to MySQL 3.23.33 last week.
>How-To-Repeat:
Start Mysql with root user or with the CAP_SCHED_MGT privilege. Do a high
volume of select/insert/replace/delete (3 or 4 requests per sec). Eventually
mysqld will lock. All threads then appear to be locked on the active_sessions
table. Killing the oldest thread (and the second one some times) clears
the lock.
This seem to appear on SGI IP19 multiprocessors architecture with
IRIX 6.5.x system.
>Fix:
Run MySQL as a non-root user and DO NOT give it the CAP_SCHED_MGT privilege.
I found that it is true you need the CAP_SCHED_MGT privilege to run mysqld with
the user parameter when launched by safe_mysql as root, but you don't need it
if you run safe_mysql under the "su" command.
The matter is closed for me as this works. I now found MySQL very stable.
Thanks.
>Submitter-Id: <submitter ID>
>Originator: Super-User
>Organization: Universite de Montreal
>MySQL support: none
>Synopsis: lockups when root on SGI
>Severity: critical
>Priority: low
>Category: mysql
>Class: sw-bug
>Release: mysql-3.23.33 (Source distribution)
>Environment:
System: IRIX64 acces 6.5 04191225 IP19
Some paths: /usr/sbin/perl /sbin/make /usr/bin/cc
Compilation info: CC='cc' CFLAGS='' CXX='CC' CXXFLAGS='' LDFLAGS=''
LIBC:
-r-xr-xr-t 1 root sys 2332864 Aug 31 16:10 /lib/libc.so.1
lrwxr-xr-x 1 root sys 19 Nov 7 15:09 /usr/lib/libc.so ->
../../lib/libc.so.1
lrwxr-xr-x 1 root sys 19 Nov 7 15:12 /usr/lib/libc.so.1 ->
../../lib/libc.so.1
Configure command: ./configure --prefix=/usr/local/mysql --without-berkeley-db
Perl: This is perl, version 5.004_04 built for irix-n32
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