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Davi Arnaut e405ab1626 Bug#38941: fast mutexes in MySQL 5.1 have mutex contention when calling random() 
The problem is that MySQL's 'fast' mutex implementation uses the
random() routine to determine the spin delay. Unfortunately, the
routine interface is not thead-safe and some implementations (eg:
glibc) might use a internal lock to protect the RNG state, causing
excessive locking contention if lots of threads are spinning on
a MySQL's 'fast' mutex. The code was also misusing the value
of the RAND_MAX macro, this macro represents the largest value
that can be returned from the rand() function, not random().

The solution is to use the quite simple Park-Miller random number
generator. The initial seed is set to 1 because the previously used
generator wasn't being seeded -- the initial seed is 1 if srandom()
is not called.

Futhermore, the 'fast' mutex implementation has several shortcomings
and provides no measurable performance benefit. Therefore, its use is
not recommended unless it provides directly measurable results.


include/my_pthread.h:
  Add field to keep the RNG state.
mysys/thr_mutex.c:
  Use a palliative per-mutex rng state to determine the spin delay.
  The RNG is not thread-safe but jumping a few sequences in the RNG
  is harmless.
2008-10-15 19:21:00 -03:00
..
.cvsignore Import changeset 2000-07-31 21:29:14 +02:00
array.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
base64.c BUG#28884 - maybe a problem with malloc into base64.c 2008-01-15 16:23:14 +04:00
ChangeLog Fix skipp -> skip once and for all. 2004-06-03 11:52:54 -05:00
charset-def.c Merge maint1.mysql.com:/data/localhome/tsmith/bk/maint/50 2007-06-21 20:55:37 +02:00
charset.c Fix for server bug experienced in Maria (wrong "Truncated incorrect <var_name> 2008-02-18 23:29:39 +01:00
checksum.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
CMakeLists.txt Bug#37003 Tests sporadically crashes with embedded server 2008-06-18 13:17:15 -03:00
default.c Up-merge 5.0.66a-release changes (via 5.0) into 5.1. 2008-07-17 11:45:08 -06:00
default_modify.c Slow query log to file now displays queries with microsecond precission 2007-07-30 11:33:50 +03:00
errors.c Fix for Bug#16902. 2008-06-16 10:05:00 +02:00
hash.c Bug#37958 - test main.plugin crash on Mac OS X when selecting from EXAMPLE engine. 2008-10-01 12:21:15 +02:00
list.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
make-ccc Remove unused (and incorrect) my_lread() and my_lwrite() 2006-09-14 23:29:44 -06:00
make-conf.c Many files: 2006-12-23 20:17:15 +01:00
Makefile.am Bug#37003 Tests sporadically crashes with embedded server 2008-06-18 13:17:15 -03:00
md5.c Avoid the name conflict between the system-provided "md5.h" and the MySQL one 2007-07-19 14:14:03 +02:00
mf_arr_appstr.c Bug #20748: Configuration files should not be read more than once 2007-11-07 15:23:50 -07:00
mf_brkhant.c Many files: 2006-12-23 20:17:15 +01:00
mf_cache.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_dirname.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_fn_ext.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_format.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_getdate.c Slow query log to file now displays queries with microsecond precission 2007-07-30 11:33:50 +03:00
mf_iocache.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
mf_iocache2.c Correct bad merge, and remove version numbers from test case. 2007-08-08 12:21:04 -04:00
mf_keycache.c Bug#37302 (missing DBUG_RETURN macro in function "find_key_block" (5.0 only)) 2008-08-11 15:08:12 -06:00
mf_keycaches.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_loadpath.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_pack.c Merge from 5.0-bugteam local. 2008-08-18 13:11:55 -04:00
mf_path.c Slow query log to file now displays queries with microsecond precission 2007-07-30 11:33:50 +03:00
mf_qsort.c Fix for bug #31207: Test "join_nested" shows different strategy on IA64 2007-10-17 20:08:58 +04:00
mf_qsort2.c Many files: 2006-12-23 20:17:15 +01:00
mf_radix.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_same.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_sort.c Merge polly.(none):/home/kaa/src/maint/mysql-5.0-maint 2007-10-18 14:32:43 +04:00
mf_soundex.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_strip.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_tempdir.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_tempfile.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
mf_unixpath.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mf_util.c Many files: 2006-12-23 20:17:15 +01:00
mf_wcomp.c Many files: 2006-12-23 20:17:15 +01:00
mf_wfile.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
mulalloc.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_access.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_aes.c my_strtoll10-x86.s: 2006-12-31 01:02:27 +01:00
my_alarm.c Many files: 2006-12-23 20:17:15 +01:00
my_alloc.c Bug#38296 (low memory crash with many conditions in a query) 2008-08-11 10:10:00 -06:00
my_append.c Slow query log to file now displays queries with microsecond precission 2007-07-30 11:33:50 +03:00
my_atomic.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_bit.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_bitmap.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_chsize.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_clock.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_compress.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_conio.c Merge magare.gmz:/home/kgeorge/mysql/autopush/B29325-5.0-opt 2007-07-11 12:44:49 +03:00
my_copy.c Slow query log to file now displays queries with microsecond precission 2007-07-30 11:33:50 +03:00
my_crc32.c Many files: 2006-12-23 20:17:15 +01:00
my_create.c Merge a88-113-38-195.elisa-laajakaista.fi:/home/my/bk/mysql-5.1-main 2008-03-13 23:35:52 +02:00
my_delete.c Merge a88-113-38-195.elisa-laajakaista.fi:/home/my/bk/mysql-5.1-main 2007-12-07 22:27:48 +02:00
my_div.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_dup.c Fixed compiler warnings. 2007-03-22 20:32:07 +02:00
my_error.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_file.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_fopen.c Fixed a lot of compiler warnings and errors detected by Forte C++ on Solaris 2007-08-13 16:11:25 +03:00
my_fstream.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_gethostbyname.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-31 01:32:21 +01:00
my_gethwaddr.c mysys/my_gethwaddr.c 2007-08-09 14:56:57 +02:00
my_getncpus.c Many files: 2006-12-27 02:23:51 +01:00
my_getopt.c Fix for server bug experienced in Maria (wrong "Truncated incorrect <var_name> 2008-02-18 23:29:39 +01:00
my_getpagesize.c Many files: 2006-12-23 20:17:15 +01:00
my_getsystime.c Reverted wrong patch, fix for Windows 32bit build. 2008-02-26 18:44:04 +02:00
my_getwd.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_handler.c Fixed problem with non-synchronous error lists 2008-03-28 18:45:03 +02:00
my_handler_errors.h Fixed problem with non-synchronous error lists 2008-03-28 18:45:03 +02:00
my_init.c Merge hynda.mysql.fi:/home/my/mysql-5.1-main 2007-11-08 13:23:08 +02:00
my_largepage.c Backport of my_malloc() changes from 5.1 to make it 64-bit safe on Unix platforms. 2007-08-29 19:20:18 +04:00
my_lib.c Merge polly.(none):/home/kaa/src/maint/mysql-5.0-maint 2007-10-18 14:32:43 +04:00
my_libwrap.c Many files: 2006-12-23 20:17:15 +01:00
my_lock.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_lockmem.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_malloc.c Backport of my_malloc() changes from 5.1 to make it 64-bit safe on Unix platforms. 2007-08-29 19:20:18 +04:00
my_memmem.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_messnc.c Many files: 2006-12-23 20:17:15 +01:00
my_mkdir.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_mmap.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_net.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_netware.c Many files: 2006-12-23 20:17:15 +01:00
my_new.cc Many files: 2006-12-23 20:17:15 +01:00
my_once.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_open.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_port.c my_strtoll10-x86.s: 2006-12-31 01:02:27 +01:00
my_pread.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_pthread.c my_pthread.c: 2007-07-30 20:40:49 +02:00
my_quick.c Added casts to avoid compiler warnings and fixed a wrong type. 2007-05-31 17:45:22 +03:00
my_read.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_realloc.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_redel.c Merge mysql.com:/home/svoj/devel/mysql/BUG25521/mysql-5.0-engines 2007-03-29 22:01:51 +05:00
my_rename.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_seek.c Merge mysql.com:/home/svoj/devel/mysql/BUG27141/mysql-5.0-engines 2007-06-05 03:43:11 +05:00
my_sleep.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
my_static.c Bug#35616: memory overrun on 64-bit linux on setting large values for keybuffer-size 2008-08-19 15:56:41 +02:00
my_static.h Bug#35616: memory overrun on 64-bit linux on setting large values for keybuffer-size 2008-08-19 15:56:41 +02:00
my_symlink.c merging fixes 2008-08-26 14:31:17 +05:00
my_symlink2.c Merge mysql.com:/home/svoj/devel/mysql/BUG32111/mysql-5.0-engines 2007-11-12 15:26:37 +04:00
my_sync.c Moved a lot of old bug fixes and safe cleanups from Maria 5.1 tree to 5.1 2007-10-11 18:07:40 +03:00
my_thr_init.c Bug#34424 query_cache_debug.test leads to valgrind warnings 2008-02-26 12:03:59 -03:00
my_vle.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_wincond.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_windac.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
my_winthread.c Bug#30992 Wrong implementation of pthread_mutex_trylock() 2007-10-03 21:38:32 +02:00
my_write.c Merge polly.(none):/home/kaa/src/maint/mysql-5.0-maint 2007-10-25 08:22:14 +04:00
mysys_priv.h Slow query log to file now displays queries with microsecond precission 2007-07-30 11:33:50 +03:00
ptr_cmp.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
queues.c Fix for server bug experienced in Maria (wrong "Truncated incorrect <var_name> 2008-02-18 23:29:39 +01:00
rijndael.c my_strtoll10-x86.s: 2006-12-31 01:02:27 +01:00
safemalloc.c Bug#35616: memory overrun on 64-bit linux on setting large values for keybuffer-size 2008-08-21 06:48:28 +02:00
sha1.c Merge bk-internal.mysql.com:/home/bk/mysql-5.0 2007-01-22 14:04:40 +02:00
stacktrace.c merge fix from 5.0-bugteam 2008-09-16 15:23:07 +02:00
string.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
test_charset.c Fix doxygen warnings. 2007-08-15 17:43:08 +04:00
test_dir.c Merge mysql.com:/home/kent/bk/main/mysql-5.0 2006-12-23 20:20:40 +01:00
test_fn.c Many files: 2006-12-23 20:17:15 +01:00
test_xml.c Many files: 2006-12-23 20:17:15 +01:00
testhash.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
thr_alarm.c Avoid compilation problem on AIX. 2008-04-28 13:41:12 -04:00
thr_lock.c Merge Bug#36579 into mysql-5.1-bugteam 2008-08-25 10:57:34 -03:00
thr_mutex.c Bug#38941: fast mutexes in MySQL 5.1 have mutex contention when calling random() 2008-10-15 19:21:00 -03:00
thr_rwlock.c Many files: 2006-12-23 20:17:15 +01:00
tree.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
trie.c WL#3817: Simplify string / memory area types and make things more consistent (first part) 2007-05-10 12:59:39 +03:00
typelib.c Merged from main 5.1 2007-05-24 19:47:58 +03:00