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

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Message-ID: <007f01cf1ed8$3b8e1450$b2aa3cf0$@gmail.com>
Date:	Fri, 31 Jan 2014 17:00:27 -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: 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"?

Regards,

-Nut

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