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mm_grantable.c: Fix infinite loop due to memory fragmentation

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The search algorithm does not work with the ctz approach at all, if there
is a free range of granules that does not fit a specific allocation (i.e.
the granule allocation is fragmented) it will cause an infinite loop as
the algorithm will try to find free space from the same (free) starting
granule, causing an infinite loop.

The clz approach works for all cases, it will find the last used granule
and the search will continue from the next free granule.

Also, offsetting a full GAT must be sizeof(gat[0] - 1), which is 31 in
this case. The reason is that the upper level search function increments
the value by +1.
This commit is contained in:
Ville Juven 2024-12-05 12:17:04 +02:00 committed by Xiang Xiao
parent f313ee5715
commit fed3da9f03
1 changed files with 1 additions and 15 deletions
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16
mm/mm_gran/mm_grantable.c
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@ -232,21 +232,7 @@ failure:
{
/* Handle full GAT quickly */
tmp = 32;
}
else if (c == r.sidx)
{
/* offset of first unused when matching for free */
v = ~v;
#ifdef CONFIG_HAVE_BUILTIN_CTZ
tmp = __builtin_ctz(v);
#else
tmp = (uint32_t)((lsb_mask(v)) * DEBRUJIN_NUM) >> 27;
DEBUGASSERT(tmp < sizeof(DEBRUJIN_LUT));
tmp = DEBRUJIN_LUT[tmp];
#endif
tmp = tmp - 1; /* Ok, because v >= 1 */
tmp = 31;
}
else
{