Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932535AbbGTIiz (ORCPT ); Mon, 20 Jul 2015 04:38:55 -0400 Received: from mail-wg0-f46.google.com ([74.125.82.46]:36736 "EHLO mail-wg0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932440AbbGTIiw (ORCPT ); Mon, 20 Jul 2015 04:38:52 -0400 Date: Mon, 20 Jul 2015 10:38:47 +0200 From: Ingo Molnar To: Martin Schwidefsky Cc: Heiko Carstens , Linus Torvalds , linux-kernel@vger.kernel.org, Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Dave Hansen , Andrew Morton , Oleg Nesterov Subject: Re: [PATCH] sched, s390: Fix the fallout of increasing the offset of 'thread_struct' within 'task_struct' Message-ID: <20150720083847.GC12468@gmail.com> References: <20150718031810.GA19818@gmail.com> <20150720072037.GA3607@osiris> <20150720080032.GA12468@gmail.com> <20150720101219.79fb06bd@mschwide> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150720101219.79fb06bd@mschwide> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2652 Lines: 70 * Martin Schwidefsky wrote: > diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S > index 3238893..84062e7 100644 > --- a/arch/s390/kernel/entry.S > +++ b/arch/s390/kernel/entry.S > @@ -178,17 +178,21 @@ _PIF_WORK = (_PIF_PER_TRAP) > */ > ENTRY(__switch_to) > stmg %r6,%r15,__SF_GPRS(%r15) # store gprs of prev task > - stg %r15,__THREAD_ksp(%r2) # store kernel stack of prev > - lg %r4,__THREAD_info(%r2) # get thread_info of prev > - lg %r5,__THREAD_info(%r3) # get thread_info of next > + lgr %r1,%r2 > + aghi %r1,__TASK_thread # thread_struct of prev task > + lg %r4,__TASK_thread_info(%r2) # get thread_info of prev > + lg %r5,__TASK_thread_info(%r3) # get thread_info of next > + stg %r15,__THREAD_ksp(%r1) # store kernel stack of prev > + lgr %r1,%r3 > + aghi %r1,__TASK_thread # thread_struct of next task > lgr %r15,%r5 > aghi %r15,STACK_INIT # end of kernel stack of next > stg %r3,__LC_CURRENT # store task struct of next > stg %r5,__LC_THREAD_INFO # store thread info of next > stg %r15,__LC_KERNEL_STACK # store end of kernel stack > + lg %r15,__THREAD_ksp(%r1) # load kernel stack of next > lctl %c4,%c4,__TASK_pid(%r3) # load pid to control reg. 4 > mvc __LC_CURRENT_PID+4(4,%r0),__TASK_pid(%r3) # store pid of next > - lg %r15,__THREAD_ksp(%r3) # load kernel stack of next > lmg %r6,%r15,__SF_GPRS(%r15) # load gprs of next task > br %r14 Btw., I think we'd be slightly better off with the variant I sent: that way the offset arithmetics are done in C code and are ready in the relevant registers by the time they are used in __switch_to(). > > @@ -417,6 +421,7 @@ ENTRY(pgm_check_handler) > LAST_BREAK %r14 > lg %r15,__LC_KERNEL_STACK > lg %r14,__TI_task(%r12) > + aghi %r14,__TASK_thread # pointer to thread_struct > lghi %r13,__LC_PGM_TDB > tm __LC_PGM_ILC+2,0x02 # check for transaction abort > jz 2f Don't we also need the chunk I have: @@ -448,6 +449,7 @@ ENTRY(pgm_check_handler) nill %r10,0x007f sll %r10,2 je .Lsysc_return + ahi %r14,-__TASK_thread_struct # r14 now points to 'current' lgf %r1,0(%r10,%r1) # load address of handler routine lgr %r2,%r11 # pass pointer to pt_regs basr %r14,%r1 # branch to interrupt-handler Because the 'basr' line relies on 'r14' having task_struct, I think? But I don't really know what I'm talking about here ... Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/