From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752754Ab1LLP0T (ORCPT ); Mon, 12 Dec 2011 10:26:19 -0500 Received: from merlin.infradead.org ([205.233.59.134]:60883 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751098Ab1LLP0S convert rfc822-to-8bit (ORCPT ); Mon, 12 Dec 2011 10:26:18 -0500 Message-ID: <1323703531.21400.1.camel@twins> Subject: Re: [PATCH -rt] printk: Disable migration instead of preemption From: Peter Zijlstra To: Richard Weinberger Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de Date: Mon, 12 Dec 2011 16:25:31 +0100 In-Reply-To: <1323696956-11445-1-git-send-email-rw@linutronix.de> References: <1323696956-11445-1-git-send-email-rw@linutronix.de> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.2.1- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2011-12-12 at 14:35 +0100, Richard Weinberger wrote: > There is no need do disable preemption in vprintk(), > disable_migrate() is sufficient. > This fixes also a the following bug in -rt: > > [ 14.759233] BUG: sleeping function called from invalid context > at /home/rw/linux-rt/kernel/rtmutex.c:645 > --- > kernel/printk.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/printk.c b/kernel/printk.c > index a50af4e..13d0825 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -898,7 +898,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) > boot_delay_msec(); > printk_delay(); > > - preempt_disable(); > + migrate_disable(); > /* This stops the holder of console_sem just where we want him */ > raw_local_irq_save(flags); > this_cpu = smp_processor_id(); > @@ -1029,7 +1029,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) > out_restore_irqs: > raw_local_irq_restore(flags); > > - preempt_enable(); > + migrate_enable(); > return printed_len; > } > EXPORT_SYMBOL(printk); One has to wonder why this patch makes any difference what so ever, note how right after/before the preempt_disable/enable there's a raw_local_irq_save/restore and last time I checked those really did disable IRQs, even on -rt.