From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 10 Oct 1999 12:25:33 -0400 (EDT) From: Alexander Viro Subject: Re: locking question: do_mmap(), do_munmap() In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Manfred Spraul Cc: Andrea Arcangeli , linux-kernel@vger.rutgers.edu, Ingo Molnar , linux-mm@kvack.org List-ID: On Sun, 10 Oct 1999, Alexander Viro wrote: > > [Cc'd to mingo] > > On Sun, 10 Oct 1999, Manfred Spraul wrote: > > > I've started adding "assert_down()" and "assert_kernellocked()" macros, > > and now I don't see the login prompt any more... > > > > eg. sys_mprotect calls merge_segments without lock_kernel(). > > Manfred, Andrea - please stop it. Yes, it does and yes, it should. > Plonking the big lock around every access to VM is _not_ a solution. If > swapper doesn't use mmap_sem - _swapper_ should be fixed. How the hell > does lock_kernel() have smaller deadlock potential than > down(&mm->mmap_sem)? OK, folks. Code in swapper (unuse_process(), right?) is called only from sys_swapoff(). It's a syscall. Andrea, could you show a scenario for deadlock here? OK, some process (but not the process doing swapoff()) may have the map locked So? it is not going to release the thing - we are seriously screwed anyway (read: we already are in deadlock). We don't hold the semaphore ourselves. Andrea, post a deadlock scenario, please. -- 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/