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Bug#24751 - Possible infinit loop in init_io_cache() when insufficient memory

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- When cache memory can't be allocated size is recaclulated using 3/4 of
  the requested memory. This number is rounded up to the nearest 
  min_cache step. 
  However with the previous implementation the new cache size might
  become bigger than requested because of this rounding and thus we get
  an infinit loop.
- This patch fixes this problem by ensuring that the new cache size
  always will be smaller on the second and subsequent iterations until
  we reach min_cache.


mysys/mf_iocache.c:
  - Added mask to cachesize to ensure that algorithm always produce a 
    smaller cache size than current, until we reach 'min_cache' size.
This commit is contained in:
unknown
2007-01-11 09:40:17 +01:00
parent 0ce5985f11
commit 2cbccbfb0c
1 changed files with 4 additions and 3 deletions
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7
mysys/mf_iocache.c
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@@ -199,11 +199,11 @@ int init_io_cache(IO_CACHE *info, File file, uint cachesize,
if (type != READ_NET && type != WRITE_NET)
{
/* Retry allocating memory in smaller blocks until we get one */
cachesize=(uint) ((ulong) (cachesize + min_cache-1) &
(ulong) ~(min_cache-1));
for (;;)
{
uint buffer_block;
cachesize=(uint) ((ulong) (cachesize + min_cache-1) &
(ulong) ~(min_cache-1));
if (cachesize < min_cache)
cachesize = min_cache;
buffer_block = cachesize;
@@ -222,7 +222,8 @@ int init_io_cache(IO_CACHE *info, File file, uint cachesize,
}
if (cachesize == min_cache)
DBUG_RETURN(2); /* Can't alloc cache */
cachesize= (uint) ((long) cachesize*3/4); /* Try with less memory */
/* Try with less memory */
cachesize= (uint) ((ulong) cachesize*3/4 & (ulong)~(min_cache-1));
}
}