Rockbox

When "Gather Runtime Data" and "Load to RAM" are disabled, any operation that modifies the runtime data (e.g. play) that is followed by a database display can produce unexpected results.

Examples:
- while in WPS press Select, go to Database/Albums, select a song from an album, long press Select for context menu and go to Playlist/Insert; after the song is inserted the current database album is displayed with no tracks or am incomplete number of tracks
- browse the Database/Albums, select a song from an album and press Select two times very fast so it starts playing it and returns back to the Album song list; if the operation is fast enough the song list will be empty or incomplete

It can be reproduced on Sansa e200, Gigabeat and on the e200 Simulator.

From my investigation is probably related to reading the database files while another thread writes the updated runtime data into them. tagcache.c:get_next can return bad data if an update to the runtime data was just performed and a write is in progress. I noticed some read/write locking in tagcache.c but it covers only part of the file read/write operations.

If "Gather Runtime Data" is not enabled (no disk file write) or "Load to RAM" is enabled (no disk file read) everything work smoothly in the above scenarios because there are no overlapping file operations.