From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751723AbeACX5g (ORCPT + 1 other); Wed, 3 Jan 2018 18:57:36 -0500 Received: from out4439.biz.mail.alibaba.com ([47.88.44.39]:50031 "EHLO out4439.biz.mail.alibaba.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751693AbeACX5d (ORCPT ); Wed, 3 Jan 2018 18:57:33 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03290;MF=yang.s@alibaba-inc.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---.A2OayaM_1515023811; From: "Yang Shi" To: longman@redhat.com, tglx@linutronix.de Cc: "Yang Shi" , Subject: [PATCH 2/2 v3] lib: debugobjects: touch watchdog to avoid softlockup when !CONFIG_PREEMPT Date: Thu, 04 Jan 2018 07:56:42 +0800 Message-Id: <1515023802-54196-2-git-send-email-yang.s@alibaba-inc.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1515023802-54196-1-git-send-email-yang.s@alibaba-inc.com> References: <1515023802-54196-1-git-send-email-yang.s@alibaba-inc.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: There are nested loops on debug objects free path, sometimes it may take over hundred thousands of loops, then cause soft lockup with !CONFIG_PREEMPT occasionally, like below: NMI watchdog: BUG: soft lockup - CPU#15 stuck for 22s! [stress-ng-getde:110342] Modules linked in: binfmt_misc(E) tcp_diag(E) inet_diag(E) bonding(E) intel_rapl(E) iosf_mbi(E) x86_pkg_temp_thermal(E) coretemp(E) iTCO_wdt(E) iTCO_vendor_support(E) kvm_intel(E) kvm(E) irqbypass(E) crct10dif_pclmul(E) crc32_pclmul(E) dcdbas(E) ghash_clmulni_intel(E) aesni_intel(E) lrw(E) gf128mul(E) glue_helper(E) ablk_helper(E) ipmi_devintf(E) sg(E) cryptd(E) pcspkr(E) mei_me(E) lpc_ich(E) ipmi_si(E) mfd_core(E) mei(E) shpchp(E) wmi(E) ipmi_msghandler(E) acpi_power_meter(E) nfsd(E) auth_rpcgss(E) nfs_acl(E) lockd(E) grace(E) sunrpc(E) ip_tables(E) ext4(E) jbd2(E) mbcache(E) sd_mod(E) mgag200(E) igb(E) drm_kms_helper(E) ixgbe(E) syscopyarea(E) mdio(E) sysfillrect(E) sysimgblt(E) ptp(E) fb_sys_fops(E) pps_core(E) ttm(E) drm(E) crc32c_intel(E) i2c_algo_bit(E) i2c_core(E) megaraid_sas(E) dca(E) irq event stamp: 4340444 hardirqs last enabled at (4340443): [] _raw_spin_unlock_irqrestore+0x36/0x60 hardirqs last disabled at (4340444): [] apic_timer_interrupt+0x91/0xa0 softirqs last enabled at (4340398): [] __do_softirq+0x349/0x50e softirqs last disabled at (4340391): [] irq_exit+0xf5/0x110 CPU: 15 PID: 110342 Comm: stress-ng-getde Tainted: G E 4.9.44-003.ali3000.alios7.x86_64.debug #1 Hardware name: Dell Inc. PowerEdge R720xd/0X6FFV, BIOS 1.6.0 03/07/2013 task: ffff884cbb0d0000 task.stack: ffff884cabc70000 RIP: 0010:[] [] _raw_spin_unlock_irqrestore+0x3b/0x60 RSP: 0018:ffff884cabc77b78 EFLAGS: 00000292 RAX: ffff884cbb0d0000 RBX: 0000000000000292 RCX: 0000000000000000 RDX: ffff884cbb0d0000 RSI: 0000000000000001 RDI: 0000000000000292 RBP: ffff884cabc77b88 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: ffffffff8357a0d8 R13: ffff884cabc77bc8 R14: ffffffff8357a0d0 R15: 00000000000000fc FS: 00002aee845fd2c0(0000) GS:ffff8852bd400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000002991808 CR3: 0000005123abf000 CR4: 00000000000406e0 Stack: ffff884ff4fe0000 ffff884ff4fd8000 ffff884cabc77c00 ffffffff8141177e 0000000000000202 ffff884cbb0d0000 ffff884cabc77bc8 0000000000000006 ffff884ff4fda000 ffffffff8357a0d8 0000000000000000 91f5d976f6020b6c Call Trace: [] debug_check_no_obj_freed+0x13e/0x220 [] __free_pages_ok+0x1f1/0x5c0 [] __free_pages+0x25/0x40 [] __free_slab+0x19b/0x270 [] discard_slab+0x39/0x50 [] __slab_free+0x207/0x270 [] ___cache_free+0xa6/0xb0 [] qlist_free_all+0x47/0x80 [] quarantine_reduce+0x159/0x190 [] kasan_kmalloc+0xaf/0xc0 [] kasan_slab_alloc+0x12/0x20 [] kmem_cache_alloc+0xfa/0x360 [] ? getname_flags+0x4f/0x1f0 [] getname_flags+0x4f/0x1f0 [] getname+0x12/0x20 [] do_sys_open+0xf9/0x210 [] SyS_open+0x1e/0x20 [] entry_SYSCALL_64_fastpath+0x1f/0xc2 Code: 7f 18 53 48 8b 55 08 48 89 f3 be 01 00 00 00 e8 3c cd 92 ff 4c 89 e7 e8 f4 0e 93 ff f6 c7 02 74 1b e8 3a ac 92 ff 48 89 df 57 9d <66> 66 90 66 90 65 ff 0d d1 ff 83 7e 5b 41 5c 5d c3 48 89 df 57 The code path might be called in either atomic or non-atomic context, so touching softlockup watchdog instead of calling cond_resched() which might fall asleep. However, it is unnecessary to touch the watchdog every loop, so just touch the watchdog at every 10000 (best estimate) loops. And, introduce a new knob: /sys/kernel/debug/debug_objects/suppress_lockup. 0 value means not suppress the softlockup message by touching the watchdog, non-zero value means suppress the softlockup message. The default value is zero. Signed-off-by: Yang Shi CC: Waiman Long CC: Thomas Gleixner --- v2 --> v3: * Use debugfs_create_u32() helper API per Waiman's suggestion v1 --> v2: * Added suppress_lockup knob in debugfs per Waiman's suggestion lib/debugobjects.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/lib/debugobjects.c b/lib/debugobjects.c index 166488d..c960221 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -19,6 +19,7 @@ #include #include #include +#include #define ODEBUG_HASH_BITS 14 #define ODEBUG_HASH_SIZE (1 << ODEBUG_HASH_BITS) @@ -67,6 +68,8 @@ struct debug_bucket { static int debug_objects_allocated; static int debug_objects_freed; +static int suppress_lockup; + static void free_obj_work(struct work_struct *work); static DECLARE_WORK(debug_obj_work, free_obj_work); @@ -768,6 +771,10 @@ static void __debug_check_no_obj_freed(const void *address, unsigned long size) debug_objects_maxchain = cnt; max_loops += cnt; + + if (max_loops > 10000 && ((max_loops % 10000) == 0) + && suppress_lockup != 0) + touch_softlockup_watchdog(); } if (max_loops > debug_objects_maxloops) @@ -812,7 +819,7 @@ static int debug_stats_open(struct inode *inode, struct file *filp) static int __init debug_objects_init_debugfs(void) { - struct dentry *dbgdir, *dbgstats; + struct dentry *dbgdir, *dbgstats, *dbglockup; if (!debug_objects_enabled) return 0; @@ -826,10 +833,15 @@ static int __init debug_objects_init_debugfs(void) if (!dbgstats) goto err; + dbglockup = debugfs_create_u32("suppress_lockup", 0644, dbgdir, + &suppress_lockup); + if (!dbglockup) + goto err; + return 0; err: - debugfs_remove(dbgdir); + debugfs_remove_recursive(dbgdir); return -ENOMEM; } -- 1.8.3.1