Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759549Ab2EQBKG (ORCPT ); Wed, 16 May 2012 21:10:06 -0400 Received: from va3ehsobe004.messaging.microsoft.com ([216.32.180.14]:4188 "EHLO va3outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752141Ab2EQBKD (ORCPT ); Wed, 16 May 2012 21:10:03 -0400 X-Forefront-Antispam-Report: CIP:160.33.194.228;KIP:(null);UIP:(null);IPV:NLI;H:usculsndmail01v.am.sony.com;RD:mail01.sonyusa.com;EFVD:NLI X-SpamScore: 0 X-BigFish: VPS0(zzzz1202hzz8275bhz2fh2a8h668h839hd25h) Message-ID: <4FB44FD0.4090800@am.sony.com> Date: Wed, 16 May 2012 18:09:36 -0700 From: Frank Rowand Reply-To: User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 MIME-Version: 1.0 To: "Rowand, Frank" CC: "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "linux-rt-users@vger.kernel.org" Subject: [PATCH RT 2/2] fix printk flush of messages References: <4FB44EF1.9050809@am.sony.com> In-Reply-To: <4FB44EF1.9050809@am.sony.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-OriginatorOrg: am.sony.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1811 Lines: 57 Updates console-make-rt-friendly.patch #ifdef CONFIG_PREEMPT_RT_FULL, printk() output is never flushed by printk() because: # some liberties taken in this pseudo-code to make it easier to follow printk() vprintk() raw_spin_lock(&logbuf_lock) # increment preempt_count(): preempt_disable() result = console_trylock_for_printk() retval = 0 # lock will always be false, because preempt_count() will be >= 1 lock = ... && !preempt_count() if (lock) retval = 1 return retval # result will always be false since lock will always be false if (result) console_unlock() # this is where the printk() output would be flushed On system boot some printk() output is flushed because register_console() and tty_open() call console_unlock(). This change also fixes the problem that was previously fixed by preempt-rt-allow-immediate-magic-sysrq-output-for-preempt_rt_full.patch Signed-off-by: Frank Rowand --- kernel/printk.c | 2 1 + 1 - 0 ! 1 file changed, 1 insertion(+), 1 deletion(-) Index: b/kernel/printk.c =================================================================== --- a/kernel/printk.c +++ b/kernel/printk.c @@ -847,7 +847,7 @@ static int console_trylock_for_printk(un int retval = 0, wake = 0; #ifdef CONFIG_PREEMPT_RT_FULL int lock = !early_boot_irqs_disabled && !irqs_disabled_flags(flags) && - !preempt_count(); + (preempt_count() <= 1); #else int lock = 1; #endif -- 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/