Re: Read from file fails

[Bart Samwel]

Libor Vanek wrote:

> > Libor Vanek wrote:
> >
> > > OK - how can I "notify" userspace process? Signals are "weak" - I need
> > > to send some data (filename etc.) to process. One solution is "on this
> > > signal call this syscall and result of this syscall will be data you
> > > need" - but I'd prefer to handle this in one "action".
> >
> > My first thoughts are to make it a blocking call.
>
> You mean like:
> - send signal to user-space process
> - wait until user-space process pick ups data (filename etc.), creates copy of file (or whatever) and calls another system call that he's finished
> - let kernel to continue syscall I blocked
> ?

No, more like:

- user-space process calls syscall, which blocks.
- kernel captures a file write event, puts the info in some kind of 
queue, wakes up the user-space process and then waits for some kind of 
acknowledgement to be returned so that it may continue.
- user-space process wakes up, the syscall completes, and passes a 
filename etc. to user-space. Copies the file, and calls a syscall to 
signify "hey, I'm done with that file". This syscall wakes up the kernel 
stuff that was waiting for this acknowledgement.
- file write event continues
- repeat from start

--Bart
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