From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Rohland Subject: Re: [question] shm_nattch in sys_shmat? Date: Mon, 03 Feb 2003 20:48:33 +0100 In-Reply-To: <3E3AFA3A.6050205@us.ibm.com> (Matthew Dobson's message of "Fri, 31 Jan 2003 14:35:38 -0800") Message-ID: References: <3E3AFA3A.6050205@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: colpatch@us.ibm.com Cc: linux-mm@kvack.org, William Lee Irwin III , "Martin J. Bligh" List-ID: Hi Matthew, On Fri, 31 Jan 2003, Matthew Dobson wrote: > sys_shmat, does in fact increment shm_nattch, but only to > decrement it again a few lines later, as seen in this code > snippet. Can anyone please explain why this is? sys_shmat temporarily increases shm_nattch to make sure it's never zero: > >>> shp->shm_nattch++; Make sure shm_nattch is greater than zero. > > user_addr = (void*) do_mmap (file, addr, size, prot, map the segment which increments shm_nattch in shm_mmap accounting for the actual mapping > >>> shp->shm_nattch--; Correct it again. Greetings Christoph -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/