From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 15 Mar 2002 13:44:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 15 Mar 2002 13:44:32 -0500 Received: from nat-pool-rdu.redhat.com ([66.187.233.200]:42903 "EHLO devserv.devel.redhat.com") by vger.kernel.org with ESMTP id ; Fri, 15 Mar 2002 13:44:26 -0500 Date: Fri, 15 Mar 2002 13:44:20 -0500 From: Pete Zaitcev To: linux-kernel@vger.kernel.org Cc: schwidefsky@de.ibm.com, Pete Zaitcev Subject: 2.4.19-pre3 s390 ret_from_fork patch Message-ID: <20020315134420.F24597@devserv.devel.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Greetings: The 2.4.19-pre3 works just dandy as it is without this patch, but it is needed for O(1) scheduler. I think Martin was going to forward this into 2.5.x tree, where O(1) is standard. The problem is that schedule_tail() is supposed to unlock runqueue, but if interrupts are enabled before that happens, a timer tick may squeeze in and deadlock. I observed such situation myself. So, I would like this to be in 2.4.19 for the sake of O(1) users. Any objections? -- Pete diff -ur -X dontdiff linux-2.4.19-pre3/arch/s390/kernel/entry.S linux-2.4.19-pre3-390/arch/s390/kernel/entry.S --- linux-2.4.19-pre3/arch/s390/kernel/entry.S Tue Mar 12 10:53:36 2002 +++ linux-2.4.19-pre3-390/arch/s390/kernel/entry.S Fri Mar 15 09:18:52 2002 @@ -254,13 +254,14 @@ ret_from_fork: basr %r13,0 l %r13,.Lentry_base-.(%r13) # setup base pointer to &entry_base + # not saving R14 here because we go to sysc_return ultimately + l %r1,BASED(.Lschedtail) + basr %r14,%r1 # call schedule_tail (unlock stuff) GET_CURRENT # load pointer to task_struct to R9 stosm 24(%r15),0x03 # reenable interrupts sr %r0,%r0 # child returns 0 st %r0,SP_R2(%r15) # store return value (change R2 on stack) - l %r1,BASED(.Lschedtail) - la %r14,BASED(sysc_return) - br %r1 # call schedule_tail, return to sysc_return + b BASED(sysc_return) # # clone, fork, vfork, exec and sigreturn need glue, diff -ur -X dontdiff linux-2.4.19-pre3/arch/s390x/kernel/entry.S linux-2.4.19-pre3-390/arch/s390x/kernel/entry.S --- linux-2.4.19-pre3/arch/s390x/kernel/entry.S Tue Mar 12 10:53:36 2002 +++ linux-2.4.19-pre3-390/arch/s390x/kernel/entry.S Fri Mar 15 09:20:33 2002 @@ -240,11 +240,11 @@ # .globl ret_from_fork ret_from_fork: + brasl %r14,schedule_tail GET_CURRENT # load pointer to task_struct to R9 stosm 48(%r15),0x03 # reenable interrupts xc SP_R2(8,%r15),SP_R2(%r15) # child returns 0 - larl %r14,sysc_return - jg schedule_tail # return to sysc_return + j sysc_return # # clone, fork, vfork, exec and sigreturn need glue,