From patchwork Tue Mar 17 06:54:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Saravana Kannan X-Patchwork-Id: 11441887 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 50ECE913 for ; Tue, 17 Mar 2020 06:55:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 27BD320754 for ; Tue, 17 Mar 2020 06:55:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="B4PdTjmn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726605AbgCQGzb (ORCPT ); Tue, 17 Mar 2020 02:55:31 -0400 Received: from mail-pf1-f202.google.com ([209.85.210.202]:53299 "EHLO mail-pf1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726132AbgCQGzG (ORCPT ); Tue, 17 Mar 2020 02:55:06 -0400 Received: by mail-pf1-f202.google.com with SMTP id i26so6479923pfk.20 for ; Mon, 16 Mar 2020 23:55:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=E7+oI0v4YJiTcfxieAo+ZZx+f+6HuOczFo3lOATV4XM=; b=B4PdTjmn0c6lJeIMW8vcsIVdp4xg+iTkfxBW8URMxjsfTod/34RC00rlZ8dY9/NGHj rrKCTZusWClEMd6JNJPoxGp2JjQz3Vdcd8YYYLt20NfXX8ALy1ABiNkndW95RCqpE8hd prQy8VwzHquTUj0dlmzVMKgJZiHOcwoRwnil89BdWszSfGhsLF+e6ccAm7U7VcM+GpvA zmI9qXY0QpJJDmeCYFi7yAUGGnzoy7kTjPoTQHDso+wb2n8wl8eXnlryMojF8X+TorD1 AEuCw5Nq+ijxA2n3vndlx84VOq2VM3qpbtV13CO6bY/Gcj9J8dKvRO5GcexCO5mWqaVS ukZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=E7+oI0v4YJiTcfxieAo+ZZx+f+6HuOczFo3lOATV4XM=; b=Bl5ojoEKIceBYkVi0/u97NM+4veOFnEgFCjugUdwSFKk3cidsIr3HXY4nx1mMyh/VT Yea9AqHrJkO0660W3udURYiK8GCXsZsFrhjMb/5SMYGrcLU1AfDKkMZYHnG1nt35sD5l McU2gHTCWNn+6B7n3dmptEeck0gh//LZGwh8gJUQtRCll1upjbjcWAj9Z2k7UodJqPAF oWc1ZQ49L4RjVbvb6EUMZhrlm977iM3z+zck0lIzc0FGES+o8yA3au0j2WBkP3q9IMAh LAdNWpkgP0Ki/+ArE90ASR4F3qnxkIVorovao4gdbeqU6Hd2RctswTphzSBDegJhjIRQ qmYw== X-Gm-Message-State: ANhLgQ0DEcPmlA5WE0wFY2ShHdzMFGMwvKgbgtw0aFL5BpMsbHlbMz2R wPeNDOTepfh6Fh+JGku9kFJPtD7PsgcR3sg= X-Google-Smtp-Source: ADFU+vvIXvU94f5jKeoxuIFXK8fHLpbZJnHvhyMgI7zQmzpPqHJV9jhKFftzMx25WRb9Z932oqWKrkPXIha6jjs= X-Received: by 2002:a17:90a:d101:: with SMTP id l1mr3844319pju.130.1584428104661; Mon, 16 Mar 2020 23:55:04 -0700 (PDT) Date: Mon, 16 Mar 2020 23:54:48 -0700 In-Reply-To: <20200317065452.236670-1-saravanak@google.com> Message-Id: <20200317065452.236670-3-saravanak@google.com> Mime-Version: 1.0 References: <20200317065452.236670-1-saravanak@google.com> X-Mailer: git-send-email 2.25.1.481.gfbce0eb801-goog Subject: [PATCH v1 2/6] driver core: Fix adding device links to probing suppliers From: Saravana Kannan To: stable@vger.kernel.org, Jonathan Corbet , Greg Kroah-Hartman , "Rafael J. Wysocki" , Len Brown , Pavel Machek , Matthias Brugger Cc: Saravana Kannan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, kernel-team@android.com, "Rafael J. Wysocki" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org From: "Rafael J. Wysocki" Currently, it is not valid to add a device link from a consumer driver ->probe callback to a supplier that is still probing too, but generally this is a valid use case. For example, if the consumer has just acquired a resource that can only be available if the supplier is functional, adding a device link to that supplier right away should be safe (and even desirable arguably), but device_link_add() doesn't handle that case correctly and the initial state of the link created by it is wrong then. To address this problem, change the initial state of device links added between a probing supplier and a probing consumer to DL_STATE_CONSUMER_PROBE and update device_links_driver_bound() to skip such links on the supplier side. With this change, if the supplier probe completes first, device_links_driver_bound() called for it will skip the link state update and when it is called for the consumer, the link state will be updated to "active". In turn, if the consumer probe completes first, device_links_driver_bound() called for it will change the state of the link to "active" and when it is called for the supplier, the link status update will be skipped. However, in principle the supplier or consumer probe may still fail after the link has been added, so modify device_links_no_driver() to change device links in the "active" or "consumer probe" state to "dormant" on the supplier side and update __device_links_no_driver() to change the link state to "available" only if it is "consumer probe" or "active". Then, if the supplier probe fails first, the leftover link to the probing consumer will become "dormant" and device_links_no_driver() called for the consumer (when its probe fails) will clean it up. In turn, if the consumer probe fails first, it will either drop the link, or change its state to "available" and, in the latter case, when device_links_no_driver() is called for the supplier, it will update the link state to "dormant". [If the supplier probe fails, but the consumer probe succeeds, which should not happen as long as the consumer driver is correct, the link still will be around, but it will be "dormant" until the supplier is probed again.] Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 15cfb094160385cc0b303c4cda483caa102af654) Signed-off-by: Saravana Kannan --- Documentation/driver-api/device_link.rst | 10 +++- drivers/base/core.c | 74 +++++++++++++++++++++--- 2 files changed, 73 insertions(+), 11 deletions(-) diff --git a/Documentation/driver-api/device_link.rst b/Documentation/driver-api/device_link.rst index d6763272e747..5c7178189612 100644 --- a/Documentation/driver-api/device_link.rst +++ b/Documentation/driver-api/device_link.rst @@ -59,11 +59,15 @@ device ``->probe`` callback or a boot-time PCI quirk. Another example for an inconsistent state would be a device link that represents a driver presence dependency, yet is added from the consumer's -``->probe`` callback while the supplier hasn't probed yet: Had the driver -core known about the device link earlier, it wouldn't have probed the +``->probe`` callback while the supplier hasn't started to probe yet: Had the +driver core known about the device link earlier, it wouldn't have probed the consumer in the first place. The onus is thus on the consumer to check presence of the supplier after adding the link, and defer probing on -non-presence. +non-presence. [Note that it is valid to create a link from the consumer's +``->probe`` callback while the supplier is still probing, but the consumer must +know that the supplier is functional already at the link creation time (that is +the case, for instance, if the consumer has just acquired some resources that +would not have been available had the supplier not been functional then).] If a device link is added in the ``->probe`` callback of the supplier or consumer driver, it is typically deleted in its ``->remove`` callback for diff --git a/drivers/base/core.c b/drivers/base/core.c index b354fdd7ce75..ae2f85ca78fb 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -287,17 +287,26 @@ struct device_link *device_link_add(struct device *consumer, link->status = DL_STATE_NONE; } else { switch (supplier->links.status) { - case DL_DEV_DRIVER_BOUND: + case DL_DEV_PROBING: switch (consumer->links.status) { case DL_DEV_PROBING: /* - * Some callers expect the link creation during - * consumer driver probe to resume the supplier - * even without DL_FLAG_RPM_ACTIVE. + * A consumer driver can create a link to a + * supplier that has not completed its probing + * yet as long as it knows that the supplier is + * already functional (for example, it has just + * acquired some resources from the supplier). */ - if (flags & DL_FLAG_PM_RUNTIME) - pm_runtime_resume(supplier); - + link->status = DL_STATE_CONSUMER_PROBE; + break; + default: + link->status = DL_STATE_DORMANT; + break; + } + break; + case DL_DEV_DRIVER_BOUND: + switch (consumer->links.status) { + case DL_DEV_PROBING: link->status = DL_STATE_CONSUMER_PROBE; break; case DL_DEV_DRIVER_BOUND: @@ -317,6 +326,14 @@ struct device_link *device_link_add(struct device *consumer, } } + /* + * Some callers expect the link creation during consumer driver probe to + * resume the supplier even without DL_FLAG_RPM_ACTIVE. + */ + if (link->status == DL_STATE_CONSUMER_PROBE && + flags & DL_FLAG_PM_RUNTIME) + pm_runtime_resume(supplier); + /* * Move the consumer and all of the devices depending on it to the end * of dpm_list and the devices_kset list. @@ -508,6 +525,16 @@ void device_links_driver_bound(struct device *dev) if (link->flags & DL_FLAG_STATELESS) continue; + /* + * Links created during consumer probe may be in the "consumer + * probe" state to start with if the supplier is still probing + * when they are created and they may become "active" if the + * consumer probe returns first. Skip them here. + */ + if (link->status == DL_STATE_CONSUMER_PROBE || + link->status == DL_STATE_ACTIVE) + continue; + WARN_ON(link->status != DL_STATE_DORMANT); WRITE_ONCE(link->status, DL_STATE_AVAILABLE); } @@ -547,17 +574,48 @@ static void __device_links_no_driver(struct device *dev) if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER) __device_link_del(&link->kref); - else if (link->status != DL_STATE_SUPPLIER_UNBIND) + else if (link->status == DL_STATE_CONSUMER_PROBE || + link->status == DL_STATE_ACTIVE) WRITE_ONCE(link->status, DL_STATE_AVAILABLE); } dev->links.status = DL_DEV_NO_DRIVER; } +/** + * device_links_no_driver - Update links after failing driver probe. + * @dev: Device whose driver has just failed to probe. + * + * Clean up leftover links to consumers for @dev and invoke + * %__device_links_no_driver() to update links to suppliers for it as + * appropriate. + * + * Links with the DL_FLAG_STATELESS flag set are ignored. + */ void device_links_no_driver(struct device *dev) { + struct device_link *link; + device_links_write_lock(); + + list_for_each_entry(link, &dev->links.consumers, s_node) { + if (link->flags & DL_FLAG_STATELESS) + continue; + + /* + * The probe has failed, so if the status of the link is + * "consumer probe" or "active", it must have been added by + * a probing consumer while this device was still probing. + * Change its state to "dormant", as it represents a valid + * relationship, but it is not functionally meaningful. + */ + if (link->status == DL_STATE_CONSUMER_PROBE || + link->status == DL_STATE_ACTIVE) + WRITE_ONCE(link->status, DL_STATE_DORMANT); + } + __device_links_no_driver(dev); + device_links_write_unlock(); }