Details
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Type:
Bug
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Status: Resolved
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Priority:
Major - P3
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Resolution: Fixed
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Affects Version/s: None
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Fix Version/s: WT2.7.0
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Labels:None
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# Replies:1
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Last comment by Customer:true
Description
WiredTiger isn't aligning mutex and log structures.
Here's a test program:
$ cat t.c
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#include <inttypes.h>
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#include <stdio.h>
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#include <stdlib.h>
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__attribute__((aligned(64))) struct xx {
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int a;
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};
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typedef struct xx XX;
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struct __attribute__((aligned(64))) yy {
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int a;
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};
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typedef struct yy YY;
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int
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main(void)
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{
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XX *a;
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YY *b;
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printf("sizeof XX: %zu\n", sizeof(XX));
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a = malloc(10 * sizeof(XX));
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printf("XX array element size: %zu\n",
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(char *)&a[1] - (char *)&a[0]);
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printf("sizeof YY: %zu\n", sizeof(YY));
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b = malloc(10 * sizeof(YY));
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printf("YY array element size: %zu\n",
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(char *)&b[1] - (char *)&b[0]);
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return (0);
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}
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$ gcc48 t.c; ./a.out
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sizeof XX: 4
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XX array element size: 4
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sizeof YY: 64
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YY array element size: 64
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$ gcc5 t.c; ./a.out
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sizeof XX: 4
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XX array element size: 4
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sizeof YY: 64
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YY array element size: 64
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$ clang t.c; ./a.out
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t.c:5:16: warning: attribute 'aligned' is ignored,
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place it after "struct" to apply attribute to type
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declaration [-Wignored-attributes]
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__attribute__((aligned(64))) struct xx {
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^
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1 warning generated.
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sizeof XX: 4
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XX array element size: 4
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sizeof YY: 64
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YY array element size: 64
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Note clang complains; however, if you precede the struct declaration with a typedef:
typedef __attribute__((aligned(64))) struct xx {
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int a;
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} XX;
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typedef struct __attribute__((aligned(64))) yy {
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int a;
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} YY;
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then clang no longer detects the problem.
$ clang t.c; ./a.out
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sizeof XX: 4
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XX array element size: 4
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sizeof YY: 64
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YY array element size: 64
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WiredTiger's page-locks and log slots are not being aligned to 64B boundaries because of this problem.
Issue Links
- is depended on by
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SERVER-20060
WiredTiger changes for MongoDB 3.1.8
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- Closed
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- links to
Activity
- Comments
Author:
{u'username': u'michaelcahill', u'name': u'Michael Cahill', u'email': u'michael.cahill@mongodb.com'}Message: Merge pull request #2142 from wiredtiger/wt-2058
WT-2058: Fix mutex and log-slot alignment.Branch: develop
https://github.com/wiredtiger/wiredtiger/commit/41b6fb879efeecf055fb4d403b0491308cf8cba6