linux-kernel - RE: WaitForMultipleObjects/etc. In Kernel

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Message-ID: <008101cf1ed9$588966d0$099c3470$@gmail.com>
Date:	Fri, 31 Jan 2014 17:08:25 -0600
From:	"Network Nut" <sillystack@...il.com>
To:	"'Clemens Ladisch'" <clemens@...isch.de>
Cc:	"'Austin S. Hemmelgarn'" <ahferroin7@...il.com>,
	<linux-kernel@...r.kernel.org>
Subject: RE: WaitForMultipleObjects/etc. In Kernel


> -----Original Message-----
> From: Network Nut [mailto:sillystack@...il.com]
> Sent: Friday, January 31, 2014 5:00 PM
> To: 'Clemens Ladisch'
> Cc: 'Austin S. Hemmelgarn'; linux-kernel@...r.kernel.org
> Subject: RE: WaitForMultipleObjects/etc. In Kernel
> > -----Original Message-----
> > From: Clemens Ladisch [mailto:clemens@...isch.de]
> > Sent: Friday, January 31, 2014 4:54 PM
> > To: Network Nut
> > Cc: 'Austin S. Hemmelgarn'; linux-kernel@...r.kernel.org
> > Subject: Re: WaitForMultipleObjects/etc. In Kernel
> >
> > Network Nut wrote:
> > >> Assuming that you're porting to mainline distributions (and not
> > >> embedded devices), named SHM segments are accessible (providing
> the
> > >> accessing process has correct permissions) under /dev/shm.  You
> > >> just need to make sure that you create the segment with the right
> > >> permissions for the other processes to access it.
> > >
> > > I already know how to do named shared memory between two
> processes.
> > I only included that to describe my overall problem.
> > >
> > > The problem that I am having is how I can make three
> > > totally-independent
> > processes interact:
> > >
> > > 1. M is a master process that creates a semaphore.
> > > 2. P1 is a process that operates against the semaphore.
> > > 3. P2 is a process that operates against the semaphore.
> > > 4. It is not permissible that M be responsible for launching P1 or P2.
> > > 5.  The semaphore, one way or another, must allow itself to be
> > > specified as one of the synchronization primitives in epoll_wait()
> >
> > This general problem descripton does not say anything more than your
> > first mail.
> >
> > Use eventfd.  To share it, use a Unix domain socket created by M.
> > (This socket must be created at a well-known path.  shm_open() works
> > similarly, but that it creates a file in a RAM disk and mmap()s it is
> > just an implementation detail.)
> 
> How do I create the socket at "well-known path"?

Nevermind. I see it. 

It is the sockaddr_un.sun_path.

Thanks!

-Nut




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