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make operation cache invalidation advisory 

This patch makes operation cache invalidate advisory rather than
immediate. Operations set a mark on cache entries meaning "this entry is
no longer valid", then the entry is removed next time the operation
is looked up.

This breaks the loop (now the cache can remove operations, but operations
can't remove cache entries), so it should be safer (I think). Everything
is inside a mutex, at least.

see https://github.com/libvips/libvips/issues/1484
This commit is contained in:
John Cupitt 2019-11-28 17:41:35 +00:00
parent 1a2a4a41f1
commit d88ce970b7
1 changed files with 38 additions and 8 deletions
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46
libvips/iofuncs/cache.c
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@ -4,6 +4,8 @@
* - try to make it compile on centos5
* 7/7/12
* - add a lock so we can run operations from many threads
* 28/11/19 [MaxKellermann]
* - make invalidate advisory rather than immediate
*/
/*
@ -131,6 +133,11 @@ typedef struct _VipsOperationCacheEntry {
* we can disconnect when we drop an operation.
*/
gulong invalidate_id;
/* Set if someone thinks this cache entry should be dropped.
*/
gboolean invalid;
} VipsOperationCacheEntry;
/* Pass in the pspec so we can get the generic type. For example, a
@ -595,7 +602,12 @@ vips_operation_touch( VipsOperation *operation )
g_hash_table_lookup( vips_cache_table, operation );
vips_cache_time += 1;
entry->time = vips_cache_time;
/* Don't up the time for invalid items -- we want them to fall out of
* cache.
*/
if( !entry->invalid )
entry->time = vips_cache_time;
}
/* Ref an operation for the cache. The operation itself, plus all the output
@ -610,6 +622,13 @@ vips_cache_ref( VipsOperation *operation )
vips_operation_touch( operation );
}
static void
vips_cache_invalidate_cb( VipsOperation *operation,
VipsOperationCacheEntry *entry )
{
entry->invalid = TRUE;
}
static void
vips_cache_insert( VipsOperation *operation )
{
@ -622,14 +641,16 @@ vips_cache_insert( VipsOperation *operation )
entry->operation = operation;
entry->time = 0;
entry->invalidate_id = 0;
entry->invalid = FALSE;
g_hash_table_insert( vips_cache_table, operation, entry );
vips_cache_ref( operation );
/* If the operation signals "invalidate", we must drop it.
/* If the operation signals "invalidate", we must tag this cache entry
* for removal.
*/
entry->invalidate_id = g_signal_connect( operation, "invalidate",
G_CALLBACK( vips_cache_remove ), NULL );
G_CALLBACK( vips_cache_invalidate_cb ), entry );
}
static void *
@ -763,13 +784,22 @@ vips_cache_operation_lookup( VipsOperation *operation )
result = NULL;
if( (hit = g_hash_table_lookup( vips_cache_table, operation )) ) {
if( vips__cache_trace ) {
printf( "vips cache*: " );
vips_object_print_summary( VIPS_OBJECT( operation ) );
if( hit->invalid ) {
/* There but has been tagged for removal.
*/
vips_cache_remove( operation );
hit = NULL;
}
else {
if( vips__cache_trace ) {
printf( "vips cache*: " );
vips_object_print_summary(
VIPS_OBJECT( operation ) );
}
result = hit->operation;
vips_cache_ref( result );
result = hit->operation;
vips_cache_ref( result );
}
}
g_mutex_unlock( vips_cache_lock );