From: Marta Rybczynska <mrybczyn@kalray.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
linux-pci@vger.kernel.org, Hari Vyas <hari.vyas@broadcom.com>,
Ray Jui <ray.jui@broadcom.com>,
Srinath Mannam <srinath.mannam@broadcom.com>,
Guenter Roeck <linux@roeck-us.net>, Jens Axboe <axboe@kernel.dk>,
Lukas Wunner <lukas@wunner.de>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
Pierre-Yves Kerbrat <pkerbrat@kalray.eu>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 5/6] pci: Protect the enable/disable state of pci_dev using the state mutex
Date: Fri, 17 Aug 2018 10:09:50 +0200 (CEST) [thread overview]
Message-ID: <66577784.13494160.1534493390262.JavaMail.zimbra@kalray.eu> (raw)
In-Reply-To: <20180817044902.31420-6-benh@kernel.crashing.org>
----- On 17 Aug, 2018, at 06:49, Benjamin Herrenschmidt benh@kernel.crashing.org wrote:
> This protects enable/disable operations using the state mutex to
> avoid races with, for example, concurrent enables on a bridge.
>
> The bus hierarchy is walked first before taking the lock to
> avoid lock nesting (though it would be ok if we ensured that
> we always nest them bottom-up, it is better to just avoid the
> issue alltogether, especially as we might find cases where
> we want to take it top-down later).
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>
> static void pci_enable_bridge(struct pci_dev *dev)
> {
> struct pci_dev *bridge;
> - int retval;
> + int retval, enabled;
>
> bridge = pci_upstream_bridge(dev);
> if (bridge)
> pci_enable_bridge(bridge);
>
> - if (pci_is_enabled(dev)) {
> - if (!dev->is_busmaster)
> - pci_set_master(dev);
> + /* Already enabled ? */
> + pci_dev_state_lock(dev);
> + enabled = pci_is_enabled(dev);
> + if (enabled && !dev->is_busmaster)
> + pci_set_master(dev);
> + pci_dev_state_unlock(dev);
> + if (enabled)
> return;
> - }
>
This looks complicated too me especially with the double locking. What do you
think about a function doing that check that used an unlocked version of
pcie_set_master?
Like:
dev_state_lock(dev);
enabled = pci_is_enabled(dev);
if (enabled && !dev->is_busmaster)
pci_set_master_unlocked();
pci_dev_state_unlock(dev);
BTW If I remember correctly the code today can set bus mastering multiple
times without checking if already done.
Marta
next prev parent reply other threads:[~2018-08-17 8:18 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-17 4:48 [RFC PATCH 0/6] pci: Rework is_added race fix and address bridge enable races Benjamin Herrenschmidt
2018-08-17 4:48 ` [RFC PATCH 1/6] Revert "PCI: Fix is_added/is_busmaster race condition" Benjamin Herrenschmidt
2018-08-17 4:57 ` Benjamin Herrenschmidt
2018-08-17 15:44 ` Bjorn Helgaas
2018-08-18 3:24 ` Benjamin Herrenschmidt
2018-08-19 2:24 ` Bjorn Helgaas
2018-08-20 2:10 ` Benjamin Herrenschmidt
2018-08-20 6:25 ` Hari Vyas
2018-08-20 11:09 ` Benjamin Herrenschmidt
2018-08-20 11:43 ` Hari Vyas
2018-08-20 7:17 ` Lukas Wunner
2018-08-20 11:12 ` Benjamin Herrenschmidt
2018-08-17 4:48 ` [RFC PATCH 2/6] pci: Set pci_dev->is_added before calling device_add Benjamin Herrenschmidt
2018-08-17 4:57 ` Benjamin Herrenschmidt
2018-08-17 16:25 ` Bjorn Helgaas
2018-08-17 18:15 ` Lukas Wunner
2018-08-18 3:41 ` Benjamin Herrenschmidt
2018-08-18 3:28 ` Benjamin Herrenschmidt
2018-08-17 4:48 ` [RFC PATCH 3/6] pci: Remove priv_flags and use dev->error_state for "disconnected" status Benjamin Herrenschmidt
2018-08-17 5:13 ` [RFC PATCH v2 " Benjamin Herrenschmidt
2018-08-17 4:49 ` [RFC PATCH 4/6] pci: Add a mutex to pci_dev to protect device state Benjamin Herrenschmidt
2018-08-17 4:49 ` [RFC PATCH 5/6] pci: Protect the enable/disable state of pci_dev using the state mutex Benjamin Herrenschmidt
2018-08-17 8:09 ` Marta Rybczynska [this message]
2018-08-17 8:30 ` Benjamin Herrenschmidt
2018-08-17 9:00 ` Hari Vyas
2018-08-17 9:39 ` Benjamin Herrenschmidt
2018-08-17 10:10 ` Hari Vyas
2018-08-17 10:24 ` Benjamin Herrenschmidt
2018-08-17 4:49 ` [RFC PATCH 6/6] pci: Protect is_busmaster using the state lock Benjamin Herrenschmidt
2018-08-17 5:03 ` [RFC PATCH 0/6] pci: Rework is_added race fix and address bridge enable races Benjamin Herrenschmidt
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