linux-kernel - [RFC PATCH 2/6] pci: Set pci_dev->is_added before calling device

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Date:   Fri, 17 Aug 2018 14:48:58 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org
Cc:     Hari Vyas <hari.vyas@...adcom.com>, Ray Jui <ray.jui@...adcom.com>,
        Srinath Mannam <srinath.mannam@...adcom.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Jens Axboe <axboe@...nel.dk>, Lukas Wunner <lukas@...ner.de>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Marta Rybczynska <mrybczyn@...ray.eu>,
        Pierre-Yves Kerbrat <pkerbrat@...ray.eu>,
        linux-kernel@...r.kernel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [RFC PATCH 2/6] pci: Set pci_dev->is_added before calling device_add

This re-fixes the bug reported by Hari Vyas <hari.vyas@...adcom.com>
after my revert of his commit but in a much simpler way.

The main issues is that is_added was being set after the driver
got bound and started, and thus setting it could race with other
changes to struct pci_dev.

This fixes it by setting the flag first, which also has the
advantage of matching the fact that we are clearing it *after*
unbinding in the remove path, thus the flag is now symtetric
and always set while the driver code is running.

Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
---
 drivers/pci/bus.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 35b7fc87eac5..48ae63673aa8 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -321,16 +321,16 @@ void pci_bus_add_device(struct pci_dev *dev)
 	pci_proc_attach_device(dev);
 	pci_bridge_d3_update(dev);
 
+	dev->is_added = 1;
 	dev->match_driver = true;
 	retval = device_attach(&dev->dev);
 	if (retval < 0 && retval != -EPROBE_DEFER) {
+		dev->is_added = 0;
 		pci_warn(dev, "device attach failed (%d)\n", retval);
 		pci_proc_detach_device(dev);
 		pci_remove_sysfs_dev_files(dev);
 		return;
 	}
-
-	dev->is_added = 1;
 }
 EXPORT_SYMBOL_GPL(pci_bus_add_device);
 
-- 
2.17.1