Details
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Bug
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Status: Closed (View Workflow)
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Minor
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Resolution: Fixed
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10.7(EOL), 10.8(EOL), 10.9(EOL), 10.10(EOL), 10.11, 11.1(EOL)
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None
Description
&= changes mem_root->flags, which makes condition always true
Probably & should be used instead of &=
mysys/my_alloc.c
if (mem_root->flags&= ROOT_FLAG_MPROTECT) <<-- |
{
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mem_root->block_size= MY_ALIGN(block_size, my_system_page_size);
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if (pre_alloc) |
pre_alloc= MY_ALIGN(pre_alloc, my_system_page_size);
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}
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Attachments
Activity
Yes, that is right, it will not make the condition always true.
By the way, can we also change this
#define MALLOC_FLAG(A) ((A & 1) ? MY_THREAD_SPECIFIC : 0)
to
#define MALLOC_FLAG(A) ((A & MY_THREAD_SPECIFIC) ? MY_THREAD_SPECIFIC : 0)
to make it a bit safer?
I'd be tempted to remove MALLOC_FLAG as its not actually used. But I'll leave that to Monty to decide in review.
This has already been fixed and pushed to 10.9
commit e1a631fecc364ce1268b13a8108a3186556d660c (HEAD -> 10.9, origin/bb-10.9-monty, origin/10.9)
Author: Monty <monty@mariadb.org>
Date: Mon Jun 12 20:11:32 2023 +0300
Fixed wrong assignment in calculate_block_sizes() for MEM_ROOT
The effect was that that ROOT_FLAG_THREAD_SPECIFIC was cleared and
the memory allocated by memroot would be contributed the the system,
not to the thread.
This exposed a bug in how "show explain for ..." allocated data.
- The thread that did provide the explain allocated data in the
"show explain" threads mem_root, which is marked as THREAD_SPECIFIC. - Fixed by allocating the explain data in a temporary explain_mem_root
which is not THREAD_SPECIFIC.
Other things:
- Added extra checks when using update_malloc_size()
- Do not call update_malloc_size() for memory not registered with
update_malloc_size(). This avoid some wrong 'memory not freed' reports. - Added a checking of 'thd->killed' to ensure that
main.truncate_notembedded.test still works.
Reported by: Yury Chaikou
Thanks Yury,
I've put you as the author of this fix on https://github.com/MariaDB/server/pull/2668.
Note, being &= it doesn't make it always true, but it does clear other flags like ROOT_FLAG_THREAD_SPECIFIC.