Re: my_thread_init
I tried reverting my change and looking at the code again -- perhaps
we have a different bug.
The function does indeed set 'id' to a non-zero value (tmp->id =
++thread_count), but then it is reset to 0 by someone else.
Let me show you:
First of all, we hit a verifier stop telling us a CS was already initialized:
=======================================
VERIFIER STOP 00000211: pid 0xEEC: Critical section is already initialized.
03338FA0 : Critical section address.
03DF2FE0 : Critical section debug info address.
00000000 : First initialization stack trace. Use dps to dump
it if non-NULL
00000000 : Not used.
=======================================
Let's look at the current call stack to see who is attempting to
re-initialize it:
0012f5e8 009ff49e 03338fa0 0012f62c 00cccccc
kernel32!InitializeCriticalSection+0xe
0012f608 0089670f cccccccc cccccccc cccccccc
mysqld!my_thread_init+0x6e <-- here.
0012f624 008745f9 0012f654 00000001 00000000 mysqld!myxt_create_thread+0x1f
0012f648 004d46f5 04669f60 0012f6e4 0012f6ac mysqld!pbxt_init+0x3f9
<-- from PBXT
0012f6a0 00471f97 03ccbbc8 0012f86c 0012f784
mysqld!ha_initialize_handlerton+0xa5
0012f6e4 00471cf1 03ccbbc8 cccccccc 00000000 mysqld!plugin_initialize+0x67
0012f86c 00447d44 00eae4d8 03f15cf8 00000000 mysqld!plugin_init+0x541
0012fb7c 0044595c 0012ff6c 0012fd44 cccccccc mysqld!init_server_components+0x5c4
0012fd30 00448a08 0000000b 03cdae70 0012ff6c mysqld!win_main+0x1cc
0012fd40 00448d7a 00000000 00250178 00000000 mysqld!mysql_service+0x38
0012ff6c 00401137 0000000b 03cdae70 03cdce10 mysqld!main+0x35a
0012ffb8 0040100f 0012fff0 7c817077 00250178 mysqld!__tmainCRTStartup+0x117
0012ffc0 7c817077 00250178 00000000 7ffd4000 mysqld!mainCRTStartup+0xf
0012fff0 00000000 00401000 00000000 78746341 kernel32!BaseProcessStart+0x23
Now let's see who initialized it first:
0x7c809f9f: kernel32!InitializeCriticalSection+0xE
0x009ff49e: mysqld!my_thread_init+0x6E <-- here
0x009ff077: mysqld!my_thread_global_init+0x77
0x009f4c9b: mysqld!my_init+0x9B
0x004457c7: mysqld!win_main+0x37
0x00448a08: mysqld!mysql_service+0x38
0x00448d7a: mysqld!main+0x35A
0x00401137: mysqld!__tmainCRTStartup+0x117
0x0040100f: mysqld!mainCRTStartup+0xF
0x7c817077: kernel32!BaseProcessStart+0x23
Looks like its called during process startup/initialization.
Let's look at *tmp at this point in time:
Local var @ 0x12f600 Type st_my_thread_var*
0x03338f70
+0x000 thr_errno : 13
+0x004 suspend : pthread_cond_t
+0x030 mutex : _RTL_CRITICAL_SECTION
+0x048 current_mutex : (null)
+0x04c current_cond : (null)
+0x050 pthread_self : (null)
+0x054 id : 0 <-- ID is zero!
+0x058 cmp_length : 0
+0x05c abort : 0
+0x060 init : 1 '' <-- but it is initialized!
+0x064 next : (null)
+0x068 prev : (null)
+0x06c opt_info : (null)
+0x070 lock_type : 0
+0x074 stack_ends_here : 0x000e7590
+0x078 mutex_in_use : (null)
+0x07c dbug : 0x03eecfc8
+0x080 name : [11] "t...@1" <-- notice the name has @1,
so its ID _was_ set at some point.
So it was reset by someone else, after being initialized, causing the
"if (THR_KEY_mysys.id)" to fail and re-initialize the CSs (there's
more than one).
So let's see who is writing to it: (by setting a data breakpoint on
0x03338f70+0x054)
ChildEBP RetAddr
0012f608 008967fa mysqld!THD::store_globals+0xa4 <-- here
0012f624 008745f9 mysqld!myxt_create_thread+0x10a
0012f648 004d46f5 mysqld!pbxt_init+0x3f9
0012f6a0 00471f97 mysqld!ha_initialize_handlerton+0xa5
0012f6e4 00471cf1 mysqld!plugin_initialize+0x67
0012f86c 00447d44 mysqld!plugin_init+0x541
0012fb7c 0044595c mysqld!init_server_components+0x5c4
0012fd30 00448a08 mysqld!win_main+0x1cc
0012fd40 00448d7a mysqld!mysql_service+0x38
0012ff6c 00401137 mysqld!main+0x35a
0012ffb8 0040100f mysqld!__tmainCRTStartup+0x117
0012ffc0 7c817077 mysqld!mainCRTStartup+0xf
0012fff0 00000000 kernel32!BaseProcessStart+0x23
THD::store_globals() does the following:
mysys_var=my_thread_var;
mysys_var->id= thread_id; // Let's see what this->thread_id is.
2:005> ?? this->thread_id
unsigned long 0
So here it gets set to 0, and hence our code fails.
Do you know why this might be?
- Alex
On Sat, Jan 30, 2010 at 9:40 AM, Alex Budovski <abudov...@gmail.com> wrote:
> Hi,
>
>> I looked at the original bug report and can't see how this bug fix
>> have anything to the with the real problem.
>>
>> I have now done a proper fix for this. Can you please test that things
>> reported in http://bugs.mysql.com/bug.php?id=31173 now works
>> on windows ?
>>
>
> Yes, looks like the change works. Thanks for fixing it!
>
>>
>>> === modified file 'mysys/my_thr_init.c'
>>> --- mysys/my_thr_init.c 2010-01-29 10:45:51 +0000
>>> +++ mysys/my_thr_init.c 2010-01-29 14:32:36 +0000
>>> @@ -317,7 +317,7 @@
>>> /*
>>> Skip initialization if the thread specific variable is already
>>> initialized
>>> */
>>> - if (THR_KEY_mysys.id)
>>> + if (THR_KEY_mysys.init)
>>> goto end;
>>> tmp= &THR_KEY_mysys;
>>> #endif
>>
>> I don't see checking the id would not work, as the id is guaranteed to
>> always be > 0
>
> Hmm.. If I recall correctly, id was in fact 0 when I ran it through a
> debugger.
>
> The reason I think the field was incorrect is because the function does
>
> tmp->init= 1;
>
> to signify that the thread-local variable has been initialized. (Where
> tmp == &THR_KEY_mysys).
>
> But the check to prevent re-initialization checks a completely
> different field (id), and when I was debugging it, was 0 at the time,
> causing the code to be entered again.
>
>>
>> The only difference I see is that if you call my_thread_end() then
>> init will be reset so it will be safe to call my_thread_init() again.
>>
>> I will do the change based on this assumption.
>>
>> If there is another reason for this change, please let me know.
>>
>> <cut>
>>
>> All other things looked good.
>>
>> I am now applying all your changes except the above, as a diff but
>> with your comments, to MariaDB 5.1. I will push it later today.
>>
>
> Thanks a lot!
>
> - Alex
>
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