Comment 61 for bug 1053959

Hi Chris,

I'm afraid I don't understand the protocol/library/guarantees well enough to interpret what you're saying with 100% confidence.

The behaviour that I'm seeing is not consistent with one app DOSing itself. Chromium goes black, I restart Chromium (with the same tabs open), it's still black. I kill and restart the X server, restart Chromium again (with the same tabs open), and now it works again (for ~8-24 hours until the same thing happens again).

I think you're saying that individual clients are allowed to allocate pixmaps out of the (very) limited mmaped space that is video RAM for this card and shared between app apps. And it's possible for a client to leak this space (it seems that maybe AWN or some of its applets does this), which eventually results in a DoS for other X apps (gnome-terminal, chromium) and makes the desktop unusable.

My view is that if clients can do this, it represents a violation of X's responsibility to maintain stability of the desktop for all clients, in a way that doesn't seem to be consistent with the behaviour of X's behaviour with any other graphics driver.

If clients can quite easily exhaust that resource, I don't think they should be allowed to allocate it at all. Why does the X server allow clients to allocate direct mapping pixmaps? What if the X server managed the graphics card's mapped memory, and decided for itself which pixmaps are actually mapped into the limited space available?

One of the reasons that I prefer X over for example Windows is that it has always tried to protect itself against badly behaved apps crashing the desktop. If that is no longer the case, it annoys me quite a bit. Do you think this is a deeper bug in X that needs to be fixed?

Cheers, Chris.