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Re: Re: [ntdev] Question about asynchronous IO

Maxim_S._ShatskihMaxim_S._Shatskih Member Posts: 10,396
>are completly 2 different stories. Even driver don’t support any IRP asynchronous processing, the
>user mode asynchronous is also supported, becase the support just comes from OS.

Not so.

If the driver _always blocks_ in the dispatch path and then completes the IRP in it without pending - then it kills overlapped IO on its handles.

In such a case, even though the overlapped IO from user will still work, it will lose its important behavior of "returning from read/write/IOCTL syscall ASAP". Instead, it will always block till the very completion.

Maxim S. Shatskih
Microsoft MVP on File System And Storage
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