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Fixing missing cache flag reset when a single entry is removed in low memory situations.

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Copied from Perforce
 Change: 190199
 ServerID: perforce.ravenbrook.com
This commit is contained in:
Richard Brooksby 2016-03-19 14:11:26 +00:00
parent ff69c9af04
commit d280ff5c04
1 changed files with 53 additions and 35 deletions
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88
mps/code/shield.c
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@ -103,23 +103,27 @@ static void protLower(Arena arena, Seg seg, AccessSet mode)
}
static Seg shieldDecache(Arena arena, Index i)
{
Seg seg;
AVER(i < arena->shCacheLimit);
seg = arena->shCache[i];
AVERT(Seg, seg);
AVER(seg->cached);
arena->shCache[i] = NULL;
seg->cached = FALSE;
return seg;
}
/* shieldFlushEntry -- flush a single entry from the cache */
static void shieldFlushEntry(Arena arena, Index i)
{
Seg seg;
AVERT(Arena, arena);
seg = arena->shCache[i];
AVERT(Seg, seg);
AVER(i < arena->shCacheLimit);
AVER(seg->cached);
Seg seg = shieldDecache(arena, i);
if (!SegIsExposed(seg))
shieldSync(arena, seg);
arena->shCache[i] = NULL; /* just to make sure it can't be reused */
}
@ -182,14 +186,7 @@ static void shieldFlushEntries(Arena arena)
mode = AccessSetEMPTY;
for (i = 0; i < arena->shCacheLimit; ++i) {
Seg seg = arena->shCache[i];
AVERT(Seg, seg);
AVER(seg->cached);
seg->cached = FALSE;
arena->shCache[i] = NULL; /* ensure it can't be reused */
Seg seg = shieldDecache(arena, i);
if (!shieldSegIsSynced(seg)) {
AVER(SegSM(seg) != AccessSetEMPTY); /* can't match first iter */
SegSetPM(seg, SegSM(seg));
@ -361,6 +358,34 @@ void (ShieldEnter)(Arena arena)
}
#if defined(SHIELD_DEBUG)
static void shieldDebugCheck(Arena arena)
{
Seg seg;
Count cached = 0;
AVERT(Arena, arena);
AVER(arena->insideShield || arena->shCacheLimit == 0);
if (SegFirst(&seg, arena))
do {
if (arena->shCacheLimit == 0) {
AVER(!seg->cached);
AVER(shieldSegIsSynced(seg));
/* You can directly set protections here to see if it makes a
difference. */
/* ProtSet(SegBase(seg), SegLimit(seg), SegPM(seg)); */
} else {
if (seg->cached)
++cached;
}
} while(SegNext(&seg, arena, seg));
AVER(cached == arena->shCacheLimit);
}
#endif
/* ShieldFlush -- empty the shield cache
*
* .shield.flush: Flush empties the shield cache. This needs to be
@ -376,7 +401,15 @@ void (ShieldEnter)(Arena arena)
void (ShieldFlush)(Arena arena)
{
#ifdef SHIELD_DEBUG
shieldDebugCheck(arena);
#endif
shieldFlushEntries(arena);
/* Cache is empty so .inv.outside.depth holds */
AVER(arena->shDepth == 0);
#ifdef SHIELD_DEBUG
shieldDebugCheck(arena);
#endif
}
@ -387,33 +420,18 @@ void (ShieldLeave)(Arena arena)
ShieldFlush(arena);
/* Cache is empty so .inv.outside.depth holds */
AVER(arena->shDepth == 0);
/* Ensuring the mutator is running at this point guarantees
.inv.outside.running */
if (arena->suspended) {
ThreadRingResume(ArenaThreadRing(arena), ArenaDeadRing(arena));
arena->suspended = FALSE;
}
arena->insideShield = FALSE;
#ifdef SHIELD_DEBUG
{
Seg seg;
if (SegFirst(&seg, arena))
do {
AVER(!seg->cached);
AVER(shieldSegIsSynced(seg));
/* You can directly set protections here to see if it makes a
difference. */
ProtSet(SegBase(seg), SegLimit(seg), SegPM(seg));
} while(SegNext(&seg, arena, seg));
}
#endif
arena->insideShield = FALSE;
}
/* ShieldExpose -- allow the MPS access to a segment while denying the mutator
*
* The MPS currently does not collect concurrently, however the only thing