Race condition in BPopUpMenu leads to KDL

[pulkomandy]

This may not be easy to trigger...

We are supposed to only allow one popup menu on a given view at a time. This doesn't work perfectly however and I often manage to open two menus in Tracker: the desktop one and the specific menu for a given icon (you have to be fast to do this - right click on the desktop and then on the icon a short time after that, but before the first menu is open).

Usually this is harmless and only leads to the two menus opening. But today I went to KDL.

PANIC: vm_page_fault: unhandled page fault in kernel space at 0x706f78, ip 0x80084ba2

The panic is in wait_for_thread_etc, called by BPopUpMenu::_Go. It seems that it's trying to access invalid thread data.

I should note that I was trying to replicate the CDDA panics/corruption, so that may be the actual problem...

[waddlesplash]

Still an issue after user_memcpy changes?