Ludovic Rousseau wrote:
Le jeudi 04 septembre 2003 � 00:11:24, Michael Bender a �crit:

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?

I don't know why the drivers are not multi-threaded by default. I was not yet in the MUSCLE community at that time. But I know most of them are _not_ multi-threaded. So we just can't decide to multi-thread pcscd and break a lot of drivers.

Asking the driver is easy and backward compatible.

Yes, you're right about that, we went through the same thing in Solaris long ago when we had a bunch of non-MP-aware drivers that had to exist in the (new then) MP-enabled kernel. Unless the driver told the kernel that it was an MP-aware driver, the kernel assumed that it wasn't, and it grabbed a pretty heavy hammer lock on the system whenever it called into such a driver. It did take a while to flush out all the old non-MP drivers, and eventually I think all Solaris kernel drivers needed to be MP aware.

Maybe in a few years we'll be able to require all MUSCLE IFD
handlers are MP/MT safe.

But it's just... I don't know, it seems that the UNIX community
is fond of re-inventing and "re-discovering" old technologies
every so often and marking them as "new" and "advanced" but
only because the current crop of people have no history as to
how things were done. MP/MT drivers are a good case in point,
why weren't those drivers required to be MP/MT safe from day
one? That's a rhetorical question of course.

mike

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