From nobody Sat May 10 08:06:37 2025 Received: from mail.valinux.co.jp (mail.valinux.co.jp [210.128.90.3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 127AA179A3 for <linux-kernel@vger.kernel.org>; Thu, 10 Oct 2024 03:55:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.128.90.3 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728532530; cv=none; b=rZ4yc8aNcBYndrCvIfX2isueEDkEgzbI1ZZF8/1K5zxLoL/mDof3w/E0OK08ABshY7m8Bw8J7TOkvJWbWKc4C27vBgEFfsGuTm6HF6BPKBwkd246dsLyxo+Wi2Tp20+UCuPLcRBzRbvcvTmzv+5Q7thbBJy51nEwcS7ngpKOk2k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728532530; c=relaxed/simple; bh=fSexSEz06jcATUnQm/WxKWDa0VIL8CAgQ/5r8+pRI5s=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=AxeoXc1ZOwGTk9WVsMgy/EZf11Ux0rmNsnzXhnNkpbsKwrmlUBx7EP4ywWPvuA9h1qY9nQ+SPz1Qlw80iJx7T4z79wXislRyk1bRIW/0K1imHxNz4/cdfI4mVyyVL+aQxyT9pNfANkw1r8SviDvHJGir5xggibVrW9HbAuUZLBI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=valinux.co.jp; spf=pass smtp.mailfrom=valinux.co.jp; arc=none smtp.client-ip=210.128.90.3 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=valinux.co.jp Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=valinux.co.jp Received: from localhost (localhost [127.0.0.1]) by mail.valinux.co.jp (Postfix) with ESMTP id 29461AA28E; Thu, 10 Oct 2024 12:55:26 +0900 (JST) X-Virus-Scanned: Debian amavisd-new at valinux.co.jp Received: from mail.valinux.co.jp ([127.0.0.1]) by localhost (mail.valinux.co.jp [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 4nBG7Yl1SloE; Thu, 10 Oct 2024 12:55:26 +0900 (JST) Received: from DESKTOP-NBGHJ1C.local.valinux.co.jp (vagw.valinux.co.jp [210.128.90.14]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by mail.valinux.co.jp (Postfix) with ESMTPSA id 07967AA264; Thu, 10 Oct 2024 12:55:26 +0900 (JST) From: takakura@valinux.co.jp To: pmladek@suse.com, rostedt@goodmis.org, john.ogness@linutronix.de, senozhatsky@chromium.org Cc: linux-kernel@vger.kernel.org, Ryo Takakura <takakura@valinux.co.jp> Subject: [PATCH] printk: Allow direct printing for PREEMPT_RT during panic Date: Thu, 10 Oct 2024 12:55:11 +0900 Message-Id: <20241010035511.289657-1-takakura@valinux.co.jp> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: <linux-kernel.vger.kernel.org> List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org> List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Ryo Takakura <takakura@valinux.co.jp> If PREEMPT_RT was enabled, printing for legacy consoles are deferred by default, including after printk_legacy_allow_panic_sync() during=20 panic which allows direct printing afterwards in case of !PREEMPT_RT. As a result, printing of messages during panic for PREEMPT_RT is handled by the console_flush_on_panic() called at the end. In case if kexec was loaded, console_flush_on_panic() will not be called and starts booting into the second kernel without printing the messages. Allow direct printing for PREEMPT_RT during panic so that messages before kexec gets printed. Signed-off-by: Ryo Takakura <takakura@valinux.co.jp> --- I was not sure if the behavior of deferred printing for PREEMPT_RT=20 during panic was expected or not. I think printing messages would be=20 useful even if kexec was loaded in case if it fails. Thanks! --- kernel/printk/printk_safe.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index 2b35a9d3919d..67a0510a8e12 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -44,7 +44,7 @@ bool is_printk_legacy_deferred(void) * The per-CPU variable @printk_context can be read safely in any * context. CPU migration is always disabled when set. */ - return (force_legacy_kthread() || + return ((!this_cpu_in_panic() && force_legacy_kthread()) || this_cpu_read(printk_context) || in_nmi()); } --=20 2.34.1