Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755394Ab3DOKPI (ORCPT ); Mon, 15 Apr 2013 06:15:08 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:52436 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752993Ab3DOKPF (ORCPT ); Mon, 15 Apr 2013 06:15:05 -0400 Date: Mon, 15 Apr 2013 11:11:59 +0100 From: Catalin Marinas To: Christopher Covington Cc: Will Deacon , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-arm-msm@vger.kernel.org" Subject: Re: [PATCH v2] arm64: Fix task tracing Message-ID: <20130415101159.GA25095@localhost.cambridge.arm.com> References: <20130408153132.GQ17476@mudshark.cambridge.arm.com> <1365510814-21343-1-git-send-email-cov@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1365510814-21343-1-git-send-email-cov@codeaurora.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1355 Lines: 36 On Tue, Apr 09, 2013 at 01:33:34PM +0100, Christopher Covington wrote: > For accurate accounting pass contextidr_thread_switch the prev > task pointer, since cpu_switch_to has at that point changed the > the stack pointer. > > Signed-off-by: Christopher Covington > --- > arch/arm64/kernel/process.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 0337cdb..a49b25a 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -315,7 +315,7 @@ struct task_struct *__switch_to(struct task_struct *prev, > /* the actual thread switch */ > last = cpu_switch_to(prev, next); > > - contextidr_thread_switch(next); > + contextidr_thread_switch(prev); The original code was indeed wrong but using prev isn't any better. For a newly created thread, prev is probably 0 (if it's in a register, cpu_context has been zeroed by copy_thread()) or some random stack value. So we either use current or move the call before cpu_switch_to() (I would go for the former). -- Catalin -- 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/