From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 30 Mar 2000 12:11:02 +0200 From: Andi Kleen Subject: Re: page fault in cli / sti safe or not Message-ID: <20000330121102.A1159@fred.muc.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: ; from pnilesh@in.ibm.com on Thu, Mar 30, 2000 at 06:49:27AM +0200 Sender: owner-linux-mm@kvack.org Return-Path: To: pnilesh@in.ibm.com Cc: linux-mm@kvack.org List-ID: On Thu, Mar 30, 2000 at 06:49:27AM +0200, pnilesh@in.ibm.com wrote: > I tried to page fault in cli () / sti() , but there was no deadlock. I > had perception that a deadlock would occur. However what might have I now > believe is that age fault always ocuur in any processes context , they will > panic in interrupt handler. So when a page fault occurs the page fault > handler is called and if the page is not found in the memory then a disk > read is scheduled the faulting process is put to sleep and schedule() is > called to run new process. The schedule () implicitly calls sti() and hence > there is no deadlock. You are right. It does not make much sense though, because the locking guarantee you wanted from cli() is broken. Also there is a bug in most linux kernels that they do turn on the interrupts only after the scheduler task queue has run. Some programs do a lot of work in the scheduler tq (isdn4linux, reiserfs, in some cases the serial driver), which can cause bad interrupt latencies (often leading the SMP TLB IPI timed out messages on faster SMP boxes) -Andi -- This is like TV. I don't like TV. -- 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.eu.org/Linux-MM/