From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <37F8DCD1.E726CBBC@switchboard.ericsson.se> Date: Mon, 04 Oct 1999 18:58:57 +0200 From: Marcus Sundberg MIME-Version: 1.0 Subject: Re: MMIO regions References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: James Simmons Cc: linux-mm@kvack.org List-ID: James Simmons wrote: > > Howdy again!! > > I noticed something for SMP machines with all the dicussion about > concurrent access to memory regions. What happens when you have two > processes that have both mmapped the same MMIO region for some card. > Doesn't have to be a video card,. On a SMP machine it is possible that > both processes could access the same region at the same time. This could > cause the card to go into a indeterminate state. Even lock the machine. > Does their exist a way to handle this? Also some cards have mulitple MMIO > regions. What if a process mmaps one MMIO region of this card and another > process mmaps another MMIO region of this card. Now process one could > alter the card in such a way it could effect the results that process two > is expecting. How is this dealt with? Is it dealt with? If not what would > be a good way to handle this? AFAIK no drivers except fbcon drivers map any IO-region to userspace. //Marcus -- -------------------------------+------------------------------------ Marcus Sundberg | http://www.stacken.kth.se/~mackan/ Royal Institute of Technology | Phone: +46 707 295404 Stockholm, Sweden | E-Mail: mackan@stacken.kth.se -- 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/