From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8F49C433F5 for ; Sat, 6 Nov 2021 20:05:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB8E76112D for ; Sat, 6 Nov 2021 20:05:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234997AbhKFUH5 (ORCPT ); Sat, 6 Nov 2021 16:07:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233477AbhKFUHv (ORCPT ); Sat, 6 Nov 2021 16:07:51 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D9CEC061570 for ; Sat, 6 Nov 2021 13:05:10 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1636229107; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3LAhmyA9MVbYyu1NRCaNhJnh3QMqcX+oD7lwbOXZlsU=; b=ghhQqagYiFDUqbJD8lqxaRKoM4qsqHlKXmLNT6En0dbxkKv6hw8Eyl9JgtC2DWU0NvujeY CD2tu4j2Lj0KRhsAlyaB48zW5WNao2RwH2XPryH8sc7Frb+l1FjDIZ2iBNC1Ju/lyqSiRK Ug3dZw95cTcV7Zh8V1jBRRm24wKpTyiHQ4NFFygkjYobAZXgRneJiddi7GZFU6VPbk6JTf EO/1fOeF9Pu1l+nPS9WYC2niK2YmjZTnU0NDtXlIDGgHrmL7FNH4b/0jcsxBytZpdH6mxB Mnhu5/EJZ4EpJ4vz/YEYJU+VQ+8EeeL0hWqVBMjXilUlPEYckB9eabSel4DDvw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1636229107; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3LAhmyA9MVbYyu1NRCaNhJnh3QMqcX+oD7lwbOXZlsU=; b=oQ2NOu/DqeEw4gtqWZRpr3ngzE8Q218vI5qxYFJWYLra0/+ysBnw3R9aLzLDy18Rq0uos3 pSV5l0Dlwatrs4CA== To: Nicholas Piggin , Petr Mladek Cc: Laurent Dufour , linux-kernel@vger.kernel.org Subject: Re: Removal of printk safe buffers delays NMI context printk In-Reply-To: <1636158295.cxlln6r0kk.astroid@bobo.none> References: <1636039236.y415994wfa.astroid@bobo.none> <87ee7vki7f.fsf@jogness.linutronix.de> <1636073838.qpmyp6q17i.astroid@bobo.none> <87r1bv2aga.fsf@jogness.linutronix.de> <1636111599.wwppq55w4t.astroid@bobo.none> <87h7cqg0xk.fsf@jogness.linutronix.de> <87lf22eem7.fsf@jogness.linutronix.de> <1636158295.cxlln6r0kk.astroid@bobo.none> Date: Sat, 06 Nov 2021 21:11:07 +0106 Message-ID: <871r3tqccs.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-11-06, Nicholas Piggin wrote: > This patch seems to work, I can submit it if you'd like? It looks good to me. Thanks for identifying and fixing this regression. John Ogness > --- > arch/powerpc/kernel/watchdog.c | 6 ++++++ > include/linux/printk.h | 4 ++++ > kernel/printk/printk.c | 5 +++++ > lib/nmi_backtrace.c | 6 ++++++ > 4 files changed, 21 insertions(+) > > diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c > index 5f69ba4de1f3..c8017bc23b00 100644 > --- a/arch/powerpc/kernel/watchdog.c > +++ b/arch/powerpc/kernel/watchdog.c > @@ -227,6 +227,12 @@ static void watchdog_smp_panic(int cpu) > cpumask_clear(&wd_smp_cpus_ipi); > } > > + /* > + * Force flush any remote buffers that might be stuck in IRQ context > + * and therefore could not run their irq_work. > + */ > + printk_trigger_flush(); > + > if (hardlockup_panic) > nmi_panic(NULL, "Hard LOCKUP"); > > diff --git a/include/linux/printk.h b/include/linux/printk.h > index 85b656f82d75..9497f6b98339 100644 > --- a/include/linux/printk.h > +++ b/include/linux/printk.h > @@ -198,6 +198,7 @@ void dump_stack_print_info(const char *log_lvl); > void show_regs_print_info(const char *log_lvl); > extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; > extern asmlinkage void dump_stack(void) __cold; > +void printk_trigger_flush(void); > #else > static inline __printf(1, 0) > int vprintk(const char *s, va_list args) > @@ -274,6 +275,9 @@ static inline void dump_stack_lvl(const char *log_lvl) > static inline void dump_stack(void) > { > } > +static inline void printk_trigger_flush(void) > +{ > +} > #endif > > #ifdef CONFIG_SMP > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > index a8d0a58deebc..99221b016c68 100644 > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -3252,6 +3252,11 @@ void defer_console_output(void) > preempt_enable(); > } > > +void printk_trigger_flush(void) > +{ > + defer_console_output(); > +} > + > int vprintk_deferred(const char *fmt, va_list args) > { > int r; > diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c > index f9e89001b52e..199ab201d501 100644 > --- a/lib/nmi_backtrace.c > +++ b/lib/nmi_backtrace.c > @@ -75,6 +75,12 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, > touch_softlockup_watchdog(); > } > > + /* > + * Force flush any remote buffers that might be stuck in IRQ context > + * and therefore could not run their irq_work. > + */ > + printk_trigger_flush(); > + > clear_bit_unlock(0, &backtrace_flag); > put_cpu(); > } > -- > 2.23.0