最常见的是这个： Thread 1 Queue : com.apple.main-thread (serial) #0 0x0000000190bcb3c4 in CFRelease.cold.2 () #1 0x0000000190a2c50c in CFRelease () #2 0x00000001d194ad38 in -[PDFTileSurface releaseSurface] () #3 0x00000001d194c230 in -[PDFTilePool releasePDFTileSurface:] () #4 0x00000001d194f618 in -[PDFPageLayerTile dealloc] () #5 0x0000000190a4778c in -[__NSArrayI_Transfer dealloc] () #6 0x000000018d5d57f8 in AutoreleasePoolPage::releaseUntil () #7 0x000000018d5d5684 in objc_autoreleasePoolPop () #8 0x000000019668d43c in -[UIScrollView setContentOffset:] () #9 0x000000018dd70918 in -[NSObject(NSKeyValueObservingPrivate) _changeValueForKeys:count:maybeOldValuesDict:maybeNewValuesDict:usingBlock:] () #10 0x000000018ddd1298 in -[NSObject(NSKeyValueObservingPrivate) _changeValueForKey:key:key:usingBlock:] () #11 0x000000018ded5b28 in _NSSetPointValueAndNotify () #12 0x0000000196c49af0 in -[UIScrollView _smoothScrollSyncWithUpdateTime:] () #13 0x0000000196c491a0 in -[UIScrollView _smoothScrollWithUpdateTime:] () #14 0x0000000196c490b0 in -[UIScrollView smoothScrollDisplayLink:] () #15 0x000000026186a66c in -[DYDisplayLinkInterposer forwardDisplayLinkCallback:] () #16 0x00000001914cc77c in CA::Display::DisplayLinkItem::dispatch () #17 0x00000001914a4388 in CA::Display::DisplayLink::dispatch_items () #18 0x00000001914bb2b8 in CA::Display::DisplayLink::dispatch_deferred_display_links () #19 0x000000019671e2a8 in _UIUpdateSequenceRunNext () #20 0x000000019671b834 in schedulerStepScheduledMainSectionContinue () #21 0x00000002a437256c in UC::DriverCore::continueProcessing () #22 0x0000000190a3f1d8 in __CFMachPortPerform () #23 0x0000000190a81824 in CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION () #24 0x0000000190a8174c in __CFRunLoopDoSource1 () #25 0x0000000190a4c6e4 in __CFRunLoopRun () #26 0x0000000190a4b54c in _CFRunLoopRunSpecificWithOptions () #27 0x0000000235da7498 in GSEventRunModal () #28 0x0000000196744244 in -[UIApplication _run] () #29 0x00000001966af158 in UIApplicationMain () #30 0x00000001968bb618 in ___lldb_unnamed_symbol_1893835b0 () #31 0x0000000105a7a308 in static UIApplicationDelegate.main() () #32 0x0000000105a7a278 in static AppDelegate.$main() () #33 0x0000000105a7a3cc in main () #34 0x000000018d659c1c in start ()