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SubjectRe: [TTY] exclusive mode question

--- Denis Vlasenko <vda@ilport.com.ua> a écrit :

> On Thursday 09 June 2005 18:12, Russell King wrote:
> > On Thu, Jun 09, 2005 at 04:22:49PM +0200, moreau francis wrote:
> > > --- Frederik Deweerdt <dev.deweerdt@laposte.net> a écrit :
> > > > Le 09/06/05 13:41 +0200, moreau francis écrivit:
> > > > >
> > > > > oh ok...sorry I misunderstood TIOEXCL meaning ;)
> > > > > Do you know how I could implement such exclusive mode (the one I
> described)
> > > > ?
> > > > >
> > > > This is handled through lock files, google for LCK..ttyS0
> > > >
> > >
> > > This lock mechanism is a convention but nothing prevent a user
> application to
> > > issue a "echo foo > /dev/ttyS0" command while "LCK..ttyS0" file exists...
> >
> > Which is absolutely necessary to work if you think about an application
> > like minicom and its file transfer helpers, which may need to re-open
> > the serial port.
> >
> > TTY locking is done via lock files only, and all non-helper applications
> > must coordinate their access via the lock files. There is no other
> > mechanism.
>
> I think original reporter is saying that TIOEXCL is nearly useless then.
>

Why not using mandatory locks instead of this "weak" user lock mechanism ?

Francis





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