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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D3930C00140 for ; Mon, 15 Aug 2022 06:56:45 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4M5lSX2HZ9z3bc3 for ; Mon, 15 Aug 2022 16:56:44 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=f4H4AEBG; dkim-atps=neutral Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4M5lRs6YHzz2xmr for ; Mon, 15 Aug 2022 16:56:09 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=f4H4AEBG; dkim-atps=neutral Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4M5lRm4DZNz4xV3; Mon, 15 Aug 2022 16:56:04 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1660546564; bh=4e1xX13sWePAAoDa7lNMiMoBGqBO22OeqsZWNRorB5Q=; h=From:To:Cc:Subject:Date:From; b=f4H4AEBG6BFqqvZkoVEmRLgp5K08PLH9Wcf8Y6SnG9hhl8TuYmwQS3FFo3L+YBQ4r znxJUDXos3FaeAAZ/XkdzVt2v0Sen8jL8AWW6h2vJ0WNBRZyMa+kn8ngTPc5b/tczb ZQ4eSSIRWj3nTvOAlCCbkmp9PkD1Pewc3Yjs+cGVWmApv22WOzV42jIWyyttGOZIsU eue55i2qS3oauTuZlX+hBtQAzEeYoq5xW+x2CHpkUIoPuI5hcQh/sLdL6/fQ0LWjiP FrV/S6KTLU4IxVBlAGoNLWuJzfV/Bp606jvUNXmDVkzGGV387tMXrL4QX+hY6A5+pL b0c6sW1+yzMBA== From: Michael Ellerman To: Subject: [PATCH] powerpc/pci: Fix get_phb_number() locking Date: Mon, 15 Aug 2022 16:55:50 +1000 Message-Id: <20220815065550.1303620-1-mpe@ellerman.id.au> X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pali@kernel.org, linux@roeck-us.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" The recent change to get_phb_number() causes a DEBUG_ATOMIC_SLEEP warning on some systems: BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 1 lock held by swapper/1: #0: c157efb0 (hose_spinlock){+.+.}-{2:2}, at: pcibios_alloc_controller+0x64/0x220 Preemption disabled at: [<00000000>] 0x0 CPU: 0 PID: 1 Comm: swapper Not tainted 5.19.0-yocto-standard+ #1 Call Trace: [d101dc90] [c073b264] dump_stack_lvl+0x50/0x8c (unreliable) [d101dcb0] [c0093b70] __might_resched+0x258/0x2a8 [d101dcd0] [c0d3e634] __mutex_lock+0x6c/0x6ec [d101dd50] [c0a84174] of_alias_get_id+0x50/0xf4 [d101dd80] [c002ec78] pcibios_alloc_controller+0x1b8/0x220 [d101ddd0] [c140c9dc] pmac_pci_init+0x198/0x784 [d101de50] [c140852c] discover_phbs+0x30/0x4c [d101de60] [c0007fd4] do_one_initcall+0x94/0x344 [d101ded0] [c1403b40] kernel_init_freeable+0x1a8/0x22c [d101df10] [c00086e0] kernel_init+0x34/0x160 [d101df30] [c001b334] ret_from_kernel_thread+0x5c/0x64 This is because pcibios_alloc_controller() holds hose_spinlock but of_alias_get_id() takes of_mutex which can sleep. The hose_spinlock protects the phb_bitmap, and also the hose_list, but it doesn't need to be held while get_phb_number() calls the OF routines, because those are only looking up information in the device tree. So fix it by having get_phb_number() take the hose_spinlock itself, only where required, and then dropping the lock before returning. pcibios_alloc_controller() then needs to take the lock again before the list_add() but that's safe, the order of the list is not important. Fixes: 0fe1e96fef0a ("powerpc/pci: Prefer PCI domain assignment via DT 'linux,pci-domain' and alias") Reported-by: Guenter Roeck Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/pci-common.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c index bdd3332200c5..31de91c8359c 100644 --- a/arch/powerpc/kernel/pci-common.c +++ b/arch/powerpc/kernel/pci-common.c @@ -68,10 +68,6 @@ void __init set_pci_dma_ops(const struct dma_map_ops *dma_ops) pci_dma_ops = dma_ops; } -/* - * This function should run under locking protection, specifically - * hose_spinlock. - */ static int get_phb_number(struct device_node *dn) { int ret, phb_id = -1; @@ -108,15 +104,20 @@ static int get_phb_number(struct device_node *dn) if (!ret) phb_id = (int)(prop & (MAX_PHBS - 1)); + spin_lock(&hose_spinlock); + /* We need to be sure to not use the same PHB number twice. */ if ((phb_id >= 0) && !test_and_set_bit(phb_id, phb_bitmap)) - return phb_id; + goto out_unlock; /* If everything fails then fallback to dynamic PHB numbering. */ phb_id = find_first_zero_bit(phb_bitmap, MAX_PHBS); BUG_ON(phb_id >= MAX_PHBS); set_bit(phb_id, phb_bitmap); +out_unlock: + spin_unlock(&hose_spinlock); + return phb_id; } @@ -127,10 +128,13 @@ struct pci_controller *pcibios_alloc_controller(struct device_node *dev) phb = zalloc_maybe_bootmem(sizeof(struct pci_controller), GFP_KERNEL); if (phb == NULL) return NULL; - spin_lock(&hose_spinlock); + phb->global_number = get_phb_number(dev); + + spin_lock(&hose_spinlock); list_add_tail(&phb->list_node, &hose_list); spin_unlock(&hose_spinlock); + phb->dn = dev; phb->is_dynamic = slab_is_available(); #ifdef CONFIG_PPC64 -- 2.37.1