From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 AB4DC518143 for ; Thu, 15 Oct 2026 13:07:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792069646; cv=none; b=Hj42mvAz1YcuVZm4t6N48xgJMr32P34w43kpNFA+OFIa1fYFmldK/+jo5n+AyT6IHHWM6qpRJ9jdmpDdpF4QsuXMJpwH/XUEGFdf016/ZgL93ZwP6VbZ4GxMvFacEJwDB6Mcuh4L6DffoxOpq0FRTvxQA1agmbk2wQmBe3u4NCE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792069646; c=relaxed/simple; bh=7ij5z9QdJytT01whps8du2H8/n2+ABTVYcangWxqFTc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=c74Ufa5T/04XYHfi0xr2EhFHvscq1HBArhKxvuvgTOIrn4VX9I1DiYRrfl+L6hsMJJLc5dnSfYPK1nEIw+wGZ4ulFpM8kWU/wCSUQGwBrFpgAyIEjNexv6VqdiM4A6FM3iterf4mqj+cvj+CDPjqEO4udqsZ9yPJstjyMMzSMwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=MkCxnsgK; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=RlQoEn3c; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="MkCxnsgK"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="RlQoEn3c" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1792069643; 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; bh=j+KHqReo2og9psgRRyqQsfpDI/DpFxNVmPFO1AgRnLY=; b=MkCxnsgKBZG1+fxm7KkcSNt+pV6U/Mwuwe3eb3/ro3+tueQlpaY+occp/dLDJ7QE5BAzVt a9NWeo1/rif16/RnVwdAM/J/We4m8jkqyDlDgcOjAf3h5xUaN8YM/CAzvrkc7580QvvgFU qcnmgkWX/tULrXnEgL1RMAkAUVRTXHQ3OXn+HUUDQqE/NPR3981IojzpIW2pBomywsiuGw 6d5Ya/+itltZFFrVjPZz+5N6K4GvF47QQhku9UxNF6/o4CRTGIXvmWl9V7/Lz+SNLEhbYp 0a87W9pilMJSqF2mNvamKN4oMwF0tsrfwIGYqwOtdw02VPqG9VyVbVV0fi2gvQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1792069643; 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; bh=j+KHqReo2og9psgRRyqQsfpDI/DpFxNVmPFO1AgRnLY=; b=RlQoEn3c71YuMwMh1PIvtzXq5UBjlFZdV+ANurfngTO7V2belz1muBiXCjQmrP/mj/fDAz B0DztB1lMIk2AODQ== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Derek Barbosa , linux-kernel@vger.kernel.org Subject: [PATCH RFC printk] printk: Postpone kthread startup Date: Thu, 15 Oct 2026 15:13:23 +0206 Message-ID: <87ecdrqfhw.fsf@jogness.linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain There have been various bug reports related to SMP systems hanging on boot. The reports vary wildly but seem to have some overlap with regard to missed IPI's during SMP setup. The reports also show that reverting NBCON console usage allows the bugs to disappear. The NBCON kthreads for console printing are started very early during boot using early_initcall(). Since these kthreads are actively enabling/disabling interrupts during early boot, they may be interfering with SMP setup. Postpone kthread starting until after all arch initcalls have completed. Signed-off-by: John Ogness --- @pmladek: This patch came about from the RedHat reports we were talking about at LPC. Derek is still doing final testing, but this patch most likely fixes the issue. We probably will want this for the 7.3-hotfix in order to preempt any other surprise bug reports. It would be nice to start the kthreads sooner, but it is not worth possibly hanging some sensitive (buggy?) hardware. kernel/printk/nbcon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index f05cc90123bd4..04fdd71b37e55 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1475,7 +1475,7 @@ static int __init printk_setup_threads(void) console_list_unlock(); return 0; } -early_initcall(printk_setup_threads); +subsys_initcall(printk_setup_threads); /** * nbcon_alloc - Allocate buffers needed by the nbcon console