From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: From: Benjamin Herrenschmidt To: Bjorn Helgaas , linux-pci@vger.kernel.org Cc: Hari Vyas , Ray Jui , Srinath Mannam , Guenter Roeck , Jens Axboe , Lukas Wunner , Konstantin Khlebnikov , Marta Rybczynska , Pierre-Yves Kerbrat , linux-kernel@vger.kernel.org, Benjamin Herrenschmidt Subject: [RFC PATCH 5/6] pci: Protect the enable/disable state of pci_dev using the state mutex Date: Fri, 17 Aug 2018 14:49:01 +1000 Message-Id: <20180817044902.31420-6-benh@kernel.crashing.org> In-Reply-To: <20180817044902.31420-1-benh@kernel.crashing.org> References: <20180817044902.31420-1-benh@kernel.crashing.org> List-ID: 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 --- drivers/pci/pci.c | 51 ++++++++++++++++++++++++++++++++--------------- 1 file changed, 35 insertions(+), 16 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 62591c153999..68152de2b5a0 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1540,26 +1540,33 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars) */ int pci_reenable_device(struct pci_dev *dev) { + int rc = 0; + + pci_dev_state_lock(dev); if (pci_is_enabled(dev)) - return do_pci_enable_device(dev, (1 << PCI_NUM_RESOURCES) - 1); - return 0; + rc = do_pci_enable_device(dev, (1 << PCI_NUM_RESOURCES) - 1); + pci_dev_state_unlock(dev); + return rc; } EXPORT_SYMBOL(pci_reenable_device); 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; - } retval = pci_enable_device(dev); if (retval) @@ -1571,9 +1578,16 @@ static void pci_enable_bridge(struct pci_dev *dev) static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) { struct pci_dev *bridge; - int err; + int err = 0; int i, bars = 0; + /* Handle upstream bridges first to avoid locking issues */ + bridge = pci_upstream_bridge(dev); + if (bridge) + pci_enable_bridge(bridge); + + pci_dev_state_lock(dev); + /* * Power state could be unknown at this point, either due to a fresh * boot or a device removal call. So get the current power state @@ -1586,12 +1600,9 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); } + /* Already enabled ? */ if (atomic_inc_return(&dev->enable_cnt) > 1) - return 0; /* already enabled */ - - bridge = pci_upstream_bridge(dev); - if (bridge) - pci_enable_bridge(bridge); + goto bail; /* only skip sriov related */ for (i = 0; i <= PCI_ROM_RESOURCE; i++) @@ -1604,6 +1615,8 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) err = do_pci_enable_device(dev, bars); if (err < 0) atomic_dec(&dev->enable_cnt); + bail: + pci_dev_state_unlock(dev); return err; } @@ -1820,12 +1833,16 @@ static void do_pci_disable_device(struct pci_dev *dev) * @dev: PCI device to disable * * NOTE: This function is a backend of PCI power management routines and is - * not supposed to be called drivers. + * not supposed to be called drivers. It will keep enable_cnt and is_busmaster + * unmodified so that the resume code knows how to restore the corresponding + * command register bits. */ void pci_disable_enabled_device(struct pci_dev *dev) { + pci_dev_state_lock(dev); if (pci_is_enabled(dev)) do_pci_disable_device(dev); + pci_dev_state_unlock(dev); } /** @@ -1849,12 +1866,14 @@ void pci_disable_device(struct pci_dev *dev) dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0, "disabling already-disabled device"); + pci_dev_state_lock(dev); if (atomic_dec_return(&dev->enable_cnt) != 0) - return; + goto bail; do_pci_disable_device(dev); - dev->is_busmaster = 0; + bail: + pci_dev_state_unlock(dev); } EXPORT_SYMBOL(pci_disable_device); -- 2.17.1