From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 4 Oct 1999 14:29:14 -0400 (EDT) From: James Simmons Subject: Re: MMIO regions In-Reply-To: <14328.53659.36975.874284@dukat.scot.redhat.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: "Stephen C. Tweedie" Cc: Linux MM List-ID: On Mon, 4 Oct 1999, Stephen C. Tweedie wrote: > Hi, > > On Mon, 4 Oct 1999 11:52:50 -0400 (EDT), James Simmons > said: > > >> The kernel doesn't impose any limits against this. If you want to make > >> this impossible, then you need to add locking to the driver itself to > >> prevent multiple processes from conflicting. > > > And if the process holding the locks dies then no other process can access > > this resource. Also if the program forgets to release the lock you end up > > with other process never being able to access this piece of hardware. > > There are any number of ways to recover from this. SysV semaphores, for > example, allow you to specify UNDO when you down a semaphore, and the > semaphore will be restored automatically on process death. > > --Stephen > Okay. But none of this prevents a rogue app from hosing your system. Such a process doesn't have to bother with locks or semaphores. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://humbolt.geo.uu.nl/Linux-MM/