Ludovic Rousseau wrote:
Le mercredi 03 septembre 2003 � 20:03:19, Jean-Luc Giraud a �crit:

Hi,

What you see is probably is due to how pcscd handles multi threading. I might be wrong, but I think that pcscd acquires a lock for each call to a specific driver and only realeases it once the call is finished. Calls to a specific driver are therefore serialised. This has the great advantage of making the development of drivers much simpler (you don't have to worry about mutlithreading in the driver). The dawback is that the driver can only execute one command at a time.

I think you are right.


The easiest way would be to ask the driver using IFDHGetCapabilities()
and a new tag to see if it can be multi threaded safely or not.

But why aren't drivers multi-threaded by default rather than playing a game with asking them if they are and then doing one thing if they say yes and another if they say no?

Unless there is some common resource that a multi-slot driver needs
to access, there is reall yno reason why a multi-slot driver can't
be thread safe nor why there should be a "single slot version" and
a "multi slot version" of the same driver. And, if there is a
common resource that a driver needs to share among it's slot
instances, there are well-defined mechanisms for doing that
(mutexes and rw locks to name two).

This thread stuff is all basic computer programming 101 and it's
been around for at least a few decades, so I'm not sure why it
always seems that everyone in the Linux community always gets
so bent out of shape when the issue of threading comes up.

mike

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