From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26B57C28CC4 for ; Sat, 1 Jun 2019 13:18:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D1142272BA for ; Sat, 1 Jun 2019 13:18:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="aAazg0Bu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1142272BA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7418B6B0277; Sat, 1 Jun 2019 09:18:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6F2766B0279; Sat, 1 Jun 2019 09:18:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5E0FE6B027A; Sat, 1 Jun 2019 09:18:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) by kanga.kvack.org (Postfix) with ESMTP id 23EFA6B0277 for ; Sat, 1 Jun 2019 09:18:56 -0400 (EDT) Received: by mail-pl1-f199.google.com with SMTP id s12so6526221plr.5 for ; Sat, 01 Jun 2019 06:18:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:from:to:cc:subject:date :message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=wjLMxnUd2EejU6uvUmJhzcLKz2PMUeFF2bQIERSqwAg=; b=no3Er1V0UwaWZeXtV2CbJs8c8TSh0D2s8ML/k5uk7T5kG4P9Gm0NXIuo0n9o2NDN9/ i/ucpM028Iw+3E2KCLK036W1670kSRbf+HdLJkqLSvt8FakpqVylvr3F8qkcyq0SiUrh JIHoBZ80u5vCSUE23/WU3+MQQHrL+t8Vfd3deg3RI2O/xAzxlfz3YP/Ca472imm48AiJ I+/7gz0poybvfS0vbjp8MUMZ0OhOLlBd0SCNnPWrM9WGR0Svae+k4kOw5KT/tdOTo4ny PgsBkedjHEwF4Xwe4DphE8IZB2ooman7PWK+s4s9dF7TM6M2D76GZVlz9r1dDu1PLmQD YP2g== X-Gm-Message-State: APjAAAVMEgCafUqLwhSPuO5Gr1fVih2VKiqhWBB3vm30zw3rnKI50fQa 0AZqTjW1bTYhj/94gk8Dg2NbRk1qGLrkodFvirkMJwqXnkkbzm9xcppZNf0D1mOGgLqWaUxbqfZ AdKuHy9pdAExvLSl30KKYBGum6aMaUVFhpVIvNlS/iGWri+GiOgwPPINCs3Kh6SGHcw== X-Received: by 2002:a62:6046:: with SMTP id u67mr17117395pfb.118.1559395135787; Sat, 01 Jun 2019 06:18:55 -0700 (PDT) X-Google-Smtp-Source: APXvYqx0Bm0GtH/vFL+lsJUhj5og9MRSKG5rKPmMZxWYgHdyB9f4tUt4AZkVMWKbbZIZm5UYwDda X-Received: by 2002:a62:6046:: with SMTP id u67mr17117325pfb.118.1559395135109; Sat, 01 Jun 2019 06:18:55 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1559395135; cv=none; d=google.com; s=arc-20160816; b=KB3HM8hdMVq1hwvlp0AV/kB2pDLTMOzVRQxgOI6JhWTMZlyqg752xuen6+MSE8U+UA ezcZ1Bppk8WvNU6rP4eQbhD2oOoJLQMnrfHArRDY9hscTjYkyry9vhvLOk2Spacqezhz UJHljcxfMIqf2KtWVySMMw5kWe1DZTcVy8/3Dc8XVl34L/46j7RMixLpGn2SfLv+cQAd fEZHFGaM3cTK/aCtC5ChjQURvRjKK95jt0b6PSBfM6UVdNT/bfDg87ILvFkXi92PsbUd Jw0zvwocF9oeWntNzIo9jg1vbPZDvSPl0nbVPD9IP6TeBJBgWFEGvVX8Vd8IjzbuDswS uS4Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:dkim-signature; bh=wjLMxnUd2EejU6uvUmJhzcLKz2PMUeFF2bQIERSqwAg=; b=OMy2BbQxP/oBQWz8nm4zvWJAUZXdcjYQ75n23qIXNIOrz5K+b7h35fyfpftxGudxnn T23bT+ubjMLFGMhDann/BpbmgIswnDk+6Ngw45JdrqNecx+Og00okEx2PxXR+bsP59zo JgmtTLIEBH4leGnIe2dZCsAiiMc+ySnhaSmcfoNdmDgeED5Vp8G5WsXpZbfcqaYDqEKn 1ycLL3imkzLIm3dNTwjhZZ/suLcIs5d8nHTsofgRQbgxPO1VNWH7SC61fa+ewR8MbDY8 lNsNopttRI3WAzswtJJSCgp55K+Bd+WWQG2qXry+T09ZIL84cXrW9/3bxNKU1kbhs9Py /DnQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=aAazg0Bu; spf=pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sashal@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id p5si10181896pls.431.2019.06.01.06.18.54 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 01 Jun 2019 06:18:55 -0700 (PDT) Received-SPF: pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=aAazg0Bu; spf=pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sashal@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E714027252; Sat, 1 Jun 2019 13:18:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559395134; bh=RsMJ2gpHDXspPAgTj0ik2EwRWy/P72vcnaQQA3/im+g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aAazg0BuxDlfRJRT2NAGmCPUf69II0Icsef9WmSTpGxaIRvLN4N6ruaPk/RBep4Gf 73tz7TURcpaxDERPSsUyinERj6me/mqHlRODM1Q8Bk7m/yflyoUy8QLudBnkpdQlGL U4ngLRPOMeu1PvOQVklZlBPGud4LRT1yJpMn9/k4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: John Sperbeck , Dennis Zhou , Sasha Levin , linux-mm@kvack.org, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: [PATCH AUTOSEL 5.1 057/186] percpu: remove spurious lock dependency between percpu and sched Date: Sat, 1 Jun 2019 09:14:33 -0400 Message-Id: <20190601131653.24205-57-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190601131653.24205-1-sashal@kernel.org> References: <20190601131653.24205-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: John Sperbeck [ Upstream commit 198790d9a3aeaef5792d33a560020861126edc22 ] In free_percpu() we sometimes call pcpu_schedule_balance_work() to queue a work item (which does a wakeup) while holding pcpu_lock. This creates an unnecessary lock dependency between pcpu_lock and the scheduler's pi_lock. There are other places where we call pcpu_schedule_balance_work() without hold pcpu_lock, and this case doesn't need to be different. Moving the call outside the lock prevents the following lockdep splat when running tools/testing/selftests/bpf/{test_maps,test_progs} in sequence with lockdep enabled: ====================================================== WARNING: possible circular locking dependency detected 5.1.0-dbg-DEV #1 Not tainted ------------------------------------------------------ kworker/23:255/18872 is trying to acquire lock: 000000000bc79290 (&(&pool->lock)->rlock){-.-.}, at: __queue_work+0xb2/0x520 but task is already holding lock: 00000000e3e7a6aa (pcpu_lock){..-.}, at: free_percpu+0x36/0x260 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (pcpu_lock){..-.}: lock_acquire+0x9e/0x180 _raw_spin_lock_irqsave+0x3a/0x50 pcpu_alloc+0xfa/0x780 __alloc_percpu_gfp+0x12/0x20 alloc_htab_elem+0x184/0x2b0 __htab_percpu_map_update_elem+0x252/0x290 bpf_percpu_hash_update+0x7c/0x130 __do_sys_bpf+0x1912/0x1be0 __x64_sys_bpf+0x1a/0x20 do_syscall_64+0x59/0x400 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #3 (&htab->buckets[i].lock){....}: lock_acquire+0x9e/0x180 _raw_spin_lock_irqsave+0x3a/0x50 htab_map_update_elem+0x1af/0x3a0 -> #2 (&rq->lock){-.-.}: lock_acquire+0x9e/0x180 _raw_spin_lock+0x2f/0x40 task_fork_fair+0x37/0x160 sched_fork+0x211/0x310 copy_process.part.43+0x7b1/0x2160 _do_fork+0xda/0x6b0 kernel_thread+0x29/0x30 rest_init+0x22/0x260 arch_call_rest_init+0xe/0x10 start_kernel+0x4fd/0x520 x86_64_start_reservations+0x24/0x26 x86_64_start_kernel+0x6f/0x72 secondary_startup_64+0xa4/0xb0 -> #1 (&p->pi_lock){-.-.}: lock_acquire+0x9e/0x180 _raw_spin_lock_irqsave+0x3a/0x50 try_to_wake_up+0x41/0x600 wake_up_process+0x15/0x20 create_worker+0x16b/0x1e0 workqueue_init+0x279/0x2ee kernel_init_freeable+0xf7/0x288 kernel_init+0xf/0x180 ret_from_fork+0x24/0x30 -> #0 (&(&pool->lock)->rlock){-.-.}: __lock_acquire+0x101f/0x12a0 lock_acquire+0x9e/0x180 _raw_spin_lock+0x2f/0x40 __queue_work+0xb2/0x520 queue_work_on+0x38/0x80 free_percpu+0x221/0x260 pcpu_freelist_destroy+0x11/0x20 stack_map_free+0x2a/0x40 bpf_map_free_deferred+0x3c/0x50 process_one_work+0x1f7/0x580 worker_thread+0x54/0x410 kthread+0x10f/0x150 ret_from_fork+0x24/0x30 other info that might help us debug this: Chain exists of: &(&pool->lock)->rlock --> &htab->buckets[i].lock --> pcpu_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(pcpu_lock); lock(&htab->buckets[i].lock); lock(pcpu_lock); lock(&(&pool->lock)->rlock); *** DEADLOCK *** 3 locks held by kworker/23:255/18872: #0: 00000000b36a6e16 ((wq_completion)events){+.+.}, at: process_one_work+0x17a/0x580 #1: 00000000dfd966f0 ((work_completion)(&map->work)){+.+.}, at: process_one_work+0x17a/0x580 #2: 00000000e3e7a6aa (pcpu_lock){..-.}, at: free_percpu+0x36/0x260 stack backtrace: CPU: 23 PID: 18872 Comm: kworker/23:255 Not tainted 5.1.0-dbg-DEV #1 Hardware name: ... Workqueue: events bpf_map_free_deferred Call Trace: dump_stack+0x67/0x95 print_circular_bug.isra.38+0x1c6/0x220 check_prev_add.constprop.50+0x9f6/0xd20 __lock_acquire+0x101f/0x12a0 lock_acquire+0x9e/0x180 _raw_spin_lock+0x2f/0x40 __queue_work+0xb2/0x520 queue_work_on+0x38/0x80 free_percpu+0x221/0x260 pcpu_freelist_destroy+0x11/0x20 stack_map_free+0x2a/0x40 bpf_map_free_deferred+0x3c/0x50 process_one_work+0x1f7/0x580 worker_thread+0x54/0x410 kthread+0x10f/0x150 ret_from_fork+0x24/0x30 Signed-off-by: John Sperbeck Signed-off-by: Dennis Zhou Signed-off-by: Sasha Levin --- mm/percpu.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/percpu.c b/mm/percpu.c index 68dd2e7e73b5f..d832793bf83a1 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1738,6 +1738,7 @@ void free_percpu(void __percpu *ptr) struct pcpu_chunk *chunk; unsigned long flags; int off; + bool need_balance = false; if (!ptr) return; @@ -1759,7 +1760,7 @@ void free_percpu(void __percpu *ptr) list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list) if (pos != chunk) { - pcpu_schedule_balance_work(); + need_balance = true; break; } } @@ -1767,6 +1768,9 @@ void free_percpu(void __percpu *ptr) trace_percpu_free_percpu(chunk->base_addr, off, ptr); spin_unlock_irqrestore(&pcpu_lock, flags); + + if (need_balance) + pcpu_schedule_balance_work(); } EXPORT_SYMBOL_GPL(free_percpu); -- 2.20.1