From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S968626AbdAEI5M (ORCPT ); Thu, 5 Jan 2017 03:57:12 -0500 Received: from mga02.intel.com ([134.134.136.20]:18770 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936475AbdAEI4P (ORCPT ); Thu, 5 Jan 2017 03:56:15 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,320,1477983600"; d="scan'208";a="49536070" From: xinwu.liu@intel.com To: arnd@arndb.de, gregkh@linuxfoundation.org, tytso@mit.edu Cc: linux-kernel@vger.kernel.org, "Liu, Xinwu" Subject: [PATCH 1/1] random: fix panic caused by system_wq is not initialization Date: Thu, 5 Jan 2017 16:49:50 +0800 Message-Id: <1483606190-32584-1-git-send-email-xinwu.liu@intel.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Liu, Xinwu" While booting kernel on simulation environment(very slow), kernel panicked: [ 310.837531] BUG: unable to handle kernel NULL pointer dereference at 0000000000000102 [ 310.909223] IP: [] __queue_work+0x2d/0x440 [ 312.023898] Call Trace: [ 312.046346] [ 312.064346] [] queue_work_on+0x38/0x80 [ 312.115177] [] credit_entropy_bits+0x1bf/0x280 [ 312.168986] [] ?add_interrupt_randomness+0x1c2/0x200 [ 312.228023] [] add_interrupt_randomness+0x1c2/0x200 [ 312.285566] [] handle_irq_event_percpu+0x31/0x60 [ 312.340869] [] handle_irq_event+0x39/0x60 [ 312.390955] [] handle_edge_irq+0x90/0x150 [ 312.441039] [] handle_irq+0xad/0x180 [ 312.487388] [] ? debug_smp_processor_id+0x17/0x20 [ 312.543433] [] do_IRQ+0x57/0xf0 [ 312.586064] [] common_interrupt+0x89/0x89 [ 312.636155] [] ? __do_softirq+0x5c/0x337 [ 312.685485] [] ? __do_softirq+0xc1/0x337 [ 312.734829] [] irq_exit+0xa5/0xb0 [ 312.778935] [] do_IRQ+0x60/0xf0 [ 312.821567] [] common_interrupt+0x89/0x89 [ 312.871612] [ 312.889628] [] ? delay_tsc+0x38/0xc0 [ 312.938966] [] ? delay_tsc+0x70/0xc0 [ 312.985320] [] __const_udelay+0x27/0x30 [ 313.033907] [] timer_irq_works+0x36/0x8f [ 313.083244] [] setup_IO_APIC+0x30e/0x7da [ 313.132587] [] ? clear_IO_APIC+0x39/0x60 [ 313.181929] [] apic_bsp_setup+0x86/0x94 [ 313.230517] [] native_smp_prepare_cpus+0x26f/0x2e2 [ 313.287320] [] kernel_init_freeable+0xda/0x227 [ 313.341127] [] kernel_init+0xe/0x100 [ 313.387481] [] ret_from_fork+0x1f/0x40 [ 313.435322] [] ? rest_init+0x90/0x90 [ 313.481649] Code: 44 00 00 55 48 89 e5 41 57 41 56 41 89 fe 41 55 49 89 d5 41 54 49 89 f4 53 48 83 ec 08 89 7d d4 9c 58 f6 c4 02 0f 85 c4 02 00 00 <41> f6 84 24 02 01 00 00 01 0f 85 df 02 00 00 41 83 fe 20 0f 84 [ 313.743052] RIP [] __queue_work+0x2d/0x440 [ 313.795369] RSP [ 313.826768] CR2: 0000000000000102 [ 313.856686] --[ end trace bb738d5d79381553 ]-- [ 313.897788] Kernel panic - not syncing: Fatal exception in interrupt 1. Now, all interrupts will contribute to entropy pool. 2. System_wq is initialized by early_initcall, but before that clock event ready long time. During this period, if entropy gathering by timer interrupt cramming input pool, migration happends but system_wq isn't ready, panic hit. So, do basically check first to avoid this. Signed-off-by: Liu, Xinwu --- drivers/char/random.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index d6876d5..621fcc9 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -730,7 +730,8 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) r->entropy_total >= 2*random_read_wakeup_bits) { struct entropy_store *other = &blocking_pool; - if (other->entropy_count <= + if (likely(keventd_up()) && + other->entropy_count <= 3 * other->poolinfo->poolfracbits / 4) { schedule_work(&other->push_work); r->entropy_total = 0; -- 1.9.1