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Fix more DSA problems uncovered by the buildfarm.

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On 32-bit systems, don't try to use 64-bit DSA pointers, because the
computation of DSA_MAX_SEGMENT_SIZE overflows Size.

Cast 1 to Size before shifting it, so that the compiler doesn't
produce a result of the wrong width.

In passing, change one use of size_t to Size.
This commit is contained in:
Robert Haas 2016-12-05 10:38:08 -05:00
parent 670b3bc8f5
commit 88f626f868
2 changed files with 16 additions and 11 deletions
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4
src/backend/utils/mmgr/dsa.c
View File

@ -98,7 +98,7 @@
#define DSA_OFFSET_BITMASK (((dsa_pointer) 1 << DSA_OFFSET_WIDTH) - 1)
/* The maximum size of a DSM segment. */
#define DSA_MAX_SEGMENT_SIZE ((size_t) 1 << DSA_OFFSET_WIDTH)
#define DSA_MAX_SEGMENT_SIZE ((Size) 1 << DSA_OFFSET_WIDTH)
/* Number of pages (see FPM_PAGE_SIZE) per regular superblock. */
#define DSA_PAGES_PER_SUPERBLOCK 16
@ -1919,7 +1919,7 @@ get_best_segment(dsa_area *area, Size npages)
* The minimum contiguous size that any segment in this bin should
* have. We'll re-bin if we see segments with fewer.
*/
Size threshold = 1 << (bin - 1);
Size threshold = (Size) 1 << (bin - 1);
dsa_segment_index segment_index;
/* Search this bin for a segment with enough contiguous space. */

23
src/include/utils/dsa.h
View File

@ -24,20 +24,25 @@ struct dsa_area;
typedef struct dsa_area dsa_area;
/*
* If this system doesn't support atomic operations on 64 bit values then
* we fall back to 32 bit dsa_pointer. For testing purposes,
* USE_SMALL_DSA_POINTER can be defined to force the use of 32 bit
* dsa_pointer even on systems that support 64 bit atomics.
* If this system only uses a 32-bit value for Size, then use the 32-bit
* implementation of DSA. This limits the amount of DSA that can be created
* to something significantly less than the entire 4GB address space because
* the DSA pointer must encode both a segment identifier and an offset, but
* that shouldn't be a significant limitation in practice.
*
* If this system doesn't support atomic operations on 64-bit values, then
* we fall back to 32-bit dsa_pointer for lack of other options.
*
* For testing purposes, USE_SMALL_DSA_POINTER can be defined to force the use
* of 32-bit dsa_pointer even on systems capable of supporting a 64-bit
* dsa_pointer.
*/
#ifndef PG_HAVE_ATOMIC_U64_SUPPORT
#define SIZEOF_DSA_POINTER 4
#else
#ifdef USE_SMALL_DSA_POINTER
#if SIZEOF_SIZE_T == 4 || !defined(PG_HAVE_ATOMIC_U64_SUPPORT) || \
defined(USE_SMALL_DSA_POINTER)
#define SIZEOF_DSA_POINTER 4
#else
#define SIZEOF_DSA_POINTER 8
#endif
#endif
/*
* The type of 'relative pointers' to memory allocated by a dynamic shared