HwStorResetBus, locking, and virtual storport drivers

NTDEV
1

I believe that for virtual storport drivers, storport doesn’t acquire
locks when calling HwStorStartIo etc. I think I read that somewhere, and
I certainly get crashes under SMP when I don’t acquire the StartIo lock
myself, and I don’t get deadlocks when I do acquire the StartIo lock.

I assumed that the HwStorResetBus routine was also called with no locks
held, but as soon as I try and acquire the StartIo lock in there I
deadlock, indicating that storport is acquiring the lock for me already.

Is this documented somewhere or are we developers expected to work this
stuff out by trial and error?

Thanks

James

2

The differences between a real miniport port and a virtual miniport are poorly documented. Regarding locks, these are the only two mentions that I’m aware of.

http://msdn.microsoft.com/en-us/library/ff559166(VS.85).aspx
http://msdn.microsoft.com/en-us/library/ff567549(VS.85).aspx

3

"The differences between a real miniport port and a virtual miniport are poorly
documented. "

Not only that, they are poorly thought out. For example, if you call StorPortAllocateNoncachedExtension in a virtual miniport, it will succeed. Then, on unload, the memory will leak, because its deallocation is explicitly bypassed.