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Use AtomicRead() and AtomicWrite() to access the pcache1_g.bUnderPressure

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global, to forestall unnecessary angst from thread analyzers.

FossilOrigin-Name: 41ec85637a7fac710a3986ee78ed25a96d331a03653069bae4d9f826cc6f944a
This commit is contained in:
drh
2025-03-05 17:12:42 +00:00
parent 9f19ea83e7
commit 427e0076a9
3 changed files with 11 additions and 16 deletions
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12
src/pcache1.c
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@ -232,10 +232,6 @@ static SQLITE_WSD struct PCacheGlobal {
sqlite3_mutex *mutex; /* Mutex for accessing the following: */
PgFreeslot *pFree; /* Free page blocks */
int nFreeSlot; /* Number of unused pcache slots */
/* The following value requires a mutex to change. We skip the mutex on
** reading because (1) most platforms read a 32-bit integer atomically and
** (2) even if an incorrect value is read, no great harm is done since this
** is really just an optimization. */
int bUnderPressure; /* True if low on PAGECACHE memory */
} pcache1_g;
@ -283,7 +279,7 @@ void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
pcache1.nReserve = n>90 ? 10 : (n/10 + 1);
pcache1.pStart = pBuf;
pcache1.pFree = 0;
pcache1.bUnderPressure = 0;
AtomicStore(&pcache1.bUnderPressure,0);
while( n-- ){
p = (PgFreeslot*)pBuf;
p->pNext = pcache1.pFree;
@ -351,7 +347,7 @@ static void *pcache1Alloc(int nByte){
if( p ){
pcache1.pFree = pcache1.pFree->pNext;
pcache1.nFreeSlot--;
pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
AtomicStore(&pcache1.bUnderPressure,pcache1.nFreeSlot<pcache1.nReserve);
assert( pcache1.nFreeSlot>=0 );
sqlite3StatusHighwater(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
sqlite3StatusUp(SQLITE_STATUS_PAGECACHE_USED, 1);
@ -390,7 +386,7 @@ static void pcache1Free(void *p){
pSlot->pNext = pcache1.pFree;
pcache1.pFree = pSlot;
pcache1.nFreeSlot++;
pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
AtomicStore(&pcache1.bUnderPressure,pcache1.nFreeSlot<pcache1.nReserve);
assert( pcache1.nFreeSlot<=pcache1.nSlot );
sqlite3_mutex_leave(pcache1.mutex);
}else{
@ -521,7 +517,7 @@ void sqlite3PageFree(void *p){
*/
static int pcache1UnderMemoryPressure(PCache1 *pCache){
if( pcache1.nSlot && (pCache->szPage+pCache->szExtra)<=pcache1.szSlot ){
return pcache1.bUnderPressure;
return AtomicLoad(&pcache1.bUnderPressure);
}else{
return sqlite3HeapNearlyFull();
}