From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 434D51990BA; Thu, 6 Jun 2024 14:11:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717683117; cv=none; b=EqJ2fWjMi68GXtvJEw5WyWiVrer2iRBx4HrkuQpv9zy9lznT+TD41cVs63k2sArqUhwVAXVD5l1IwoyMMORy01ntD2aihwt7eXzWz3ElhJX5tIm3OwKZyHorM4CAgTKjSYNXhR4+LDHEtPwNI/C2jlzDdvyjzpKs3pjEyIA/QKA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717683117; c=relaxed/simple; bh=vPtXuVMP6FTHqJzKdPfiP3vdW5sgM80xY1SGK9O89Dw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lRrgfIqati8GYKt30YuAi1UoFcH5A/1vsAPZFvr2KKOwDOkEo++OiHZ6nXafRaJYO576ok+LQZIN9qATxB9CE7TXCkQDfK2ApwJPq8x7N8G/qZ4okPlhSyqFSt4lyUmP/DwVgsddpe79U1xe1hZEywnNudIEFX1saJ4lMnTqo7Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=y2kNpUiW; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="y2kNpUiW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B48BFC2BD10; Thu, 6 Jun 2024 14:11:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1717683116; bh=vPtXuVMP6FTHqJzKdPfiP3vdW5sgM80xY1SGK9O89Dw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=y2kNpUiWxDGbv+T2uBAe8OXp8H2K08QRdny+Pt7svI8OV8hxeRTRtf4veWm6IFftW VprP/FymPE3MOCXts+6Tdz6CtGAFJOUdwa/mA8ukc2QFRjYhZENgzKHzDAj7D3S5Zr 5O0hXnkK6zBIft0GeI4naCUqcQ306q513wuJHQ54= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Oleg Nesterov , Thomas Gleixner , Ingo Molnar , Phil Auld , Frederic Weisbecker , Sasha Levin Subject: [PATCH 6.6 052/744] sched/isolation: Fix boot crash when maxcpus < first housekeeping CPU Date: Thu, 6 Jun 2024 15:55:24 +0200 Message-ID: <20240606131734.110596007@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240606131732.440653204@linuxfoundation.org> References: <20240606131732.440653204@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov [ Upstream commit 257bf89d84121280904800acd25cc2c444c717ae ] housekeeping_setup() checks cpumask_intersects(present, online) to ensure that the kernel will have at least one housekeeping CPU after smp_init(), but this doesn't work if the maxcpus= kernel parameter limits the number of processors available after bootup. For example, a kernel with "maxcpus=2 nohz_full=0-2" parameters crashes at boot time on a virtual machine with 4 CPUs. Change housekeeping_setup() to use cpumask_first_and() and check that the returned CPU number is valid and less than setup_max_cpus. Another corner case is "nohz_full=0" on a machine with a single CPU or with the maxcpus=1 kernel argument. In this case non_housekeeping_mask is empty and tick_nohz_full_setup() makes no sense. And indeed, the kernel hits the WARN_ON(tick_nohz_full_running) in tick_sched_do_timer(). And how should the kernel interpret the "nohz_full=" parameter? It should be silently ignored, but currently cpulist_parse() happily returns the empty cpumask and this leads to the same problem. Change housekeeping_setup() to check cpumask_empty(non_housekeeping_mask) and do nothing in this case. Signed-off-by: Oleg Nesterov Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Reviewed-by: Phil Auld Acked-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20240413141746.GA10008@redhat.com Signed-off-by: Sasha Levin --- kernel/sched/isolation.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 373d42c707bc5..82e2f7fc7c267 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -109,6 +109,7 @@ static void __init housekeeping_setup_type(enum hk_type type, static int __init housekeeping_setup(char *str, unsigned long flags) { cpumask_var_t non_housekeeping_mask, housekeeping_staging; + unsigned int first_cpu; int err = 0; if ((flags & HK_FLAG_TICK) && !(housekeeping.flags & HK_FLAG_TICK)) { @@ -129,7 +130,8 @@ static int __init housekeeping_setup(char *str, unsigned long flags) cpumask_andnot(housekeeping_staging, cpu_possible_mask, non_housekeeping_mask); - if (!cpumask_intersects(cpu_present_mask, housekeeping_staging)) { + first_cpu = cpumask_first_and(cpu_present_mask, housekeeping_staging); + if (first_cpu >= nr_cpu_ids || first_cpu >= setup_max_cpus) { __cpumask_set_cpu(smp_processor_id(), housekeeping_staging); __cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask); if (!housekeeping.flags) { @@ -138,6 +140,9 @@ static int __init housekeeping_setup(char *str, unsigned long flags) } } + if (cpumask_empty(non_housekeeping_mask)) + goto free_housekeeping_staging; + if (!housekeeping.flags) { /* First setup call ("nohz_full=" or "isolcpus=") */ enum hk_type type; -- 2.43.0