From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lappi.waldorf-gmbh.de (cacc-14.uni-koblenz.de [141.26.131.14]) by mailhost.uni-koblenz.de (8.9.1/8.9.1) with ESMTP id TAA27055 for ; Fri, 15 Oct 1999 19:14:02 +0200 (MET DST) Date: Fri, 15 Oct 1999 11:58:16 +0200 From: Ralf Baechle Subject: Re: locking question: do_mmap(), do_munmap() Message-ID: <19991015115816.B948@uni-koblenz.de> References: <199910130125.SAA66579@google.engr.sgi.com> <380435A6.93B4B75A@colorfullife.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <380435A6.93B4B75A@colorfullife.com>; from Manfred Spraul on Wed, Oct 13, 1999 at 09:32:54AM +0200 Sender: owner-linux-mm@kvack.org Return-Path: To: Manfred Spraul Cc: Kanoj Sarcar , "Stephen C. Tweedie" , viro@math.psu.edu, andrea@suse.de, linux-kernel@vger.rutgers.edu, mingo@chiara.csoma.elte.hu, linux-mm@kvack.org, linux@engr.sgi.com, linux-mips@fnet.fr, linux-mips@vger.rutgers.edu List-ID: On Wed, Oct 13, 1999 at 09:32:54AM +0200, Manfred Spraul wrote: > Kanoj Sarcar wrote: > > Here's a primitive patch showing the direction I am thinking of. I do not > > have any problem with a spinning lock, but I coded this against 2.2.10, > > where insert_vm_struct could go to sleep, hence I had to use sleeping > > locks to protect the vma chain. > > I found a few places where I don't know how to change them. > > 1) arch/mips/mm/r4xx0.c: > their flush_cache_range() function internally calls find_vma(). > flush_cache_range() is called by proc/mem.c, and it seems that this > function cannot get the mmap semaphore. > Currently, every caller of flush_cache_range() either owns the kernel > lock or the mmap_sem. > OTHO, this function contains a race anyway [src_vma can go away if > handle_mm_fault() sleeps, src_vma is used at the end of the function.] The sole reason for fiddling with the VMA is that we try to optimize icache flushing for non-VM_EXEC vmas. This optimization is broken as the MIPS hardware doesn't make a difference between read and execute in page permissions, so the icache might be dirty even though the vma has no exec permission. So I'll have to re-implement this whole things anyway. The other problem is an efficience problem. A call like flush_cache_range(some_mm_ptr, 0, TASK_SIZE) would take a minor eternity and for MIPS64 a full eternity ... Ralf -- 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/