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PCI: pciehp: Avoid returning prematurely from sysfs requests
A sysfs request to enable or disable a PCIe hotplug slot should not
return before it has been carried out. That is sought to be achieved by
waiting until the controller's "pending_events" have been cleared.
However the IRQ thread pciehp_ist() clears the "pending_events" before
it acts on them. If pciehp_sysfs_enable_slot() / _disable_slot() happen
to check the "pending_events" after they have been cleared but while
pciehp_ist() is still running, the functions may return prematurely
with an incorrect return value.
Fix by introducing an "ist_running" flag which must be false before a sysfs
request is allowed to return.
Fixes: 32a8cef274
("PCI: pciehp: Enable/disable exclusively from IRQ thread")
Link: https://lore.kernel.org/linux-pci/1562226638-54134-1-git-send-email-wangxiongfeng2@huawei.com
Link: https://lore.kernel.org/r/4174210466e27eb7e2243dd1d801d5f75baaffd8.1565345211.git.lukas@wunner.de
Reported-and-tested-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org # v4.19+
This commit is contained in:
parent
54ecb8f702
commit
157c1062fc
@ -72,6 +72,7 @@ extern int pciehp_poll_time;
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* @reset_lock: prevents access to the Data Link Layer Link Active bit in the
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* Link Status register and to the Presence Detect State bit in the Slot
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* Status register during a slot reset which may cause them to flap
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* @ist_running: flag to keep user request waiting while IRQ thread is running
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* @request_result: result of last user request submitted to the IRQ thread
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* @requester: wait queue to wake up on completion of user request,
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* used for synchronous slot enable/disable request via sysfs
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@ -101,6 +102,7 @@ struct controller {
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struct hotplug_slot hotplug_slot; /* hotplug core interface */
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struct rw_semaphore reset_lock;
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unsigned int ist_running;
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int request_result;
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wait_queue_head_t requester;
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};
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@ -375,7 +375,8 @@ int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot)
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ctrl->request_result = -ENODEV;
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pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);
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wait_event(ctrl->requester,
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!atomic_read(&ctrl->pending_events));
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!atomic_read(&ctrl->pending_events) &&
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!ctrl->ist_running);
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return ctrl->request_result;
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case POWERON_STATE:
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ctrl_info(ctrl, "Slot(%s): Already in powering on state\n",
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@ -408,7 +409,8 @@ int pciehp_sysfs_disable_slot(struct hotplug_slot *hotplug_slot)
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mutex_unlock(&ctrl->state_lock);
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pciehp_request(ctrl, DISABLE_SLOT);
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wait_event(ctrl->requester,
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!atomic_read(&ctrl->pending_events));
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!atomic_read(&ctrl->pending_events) &&
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!ctrl->ist_running);
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return ctrl->request_result;
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case POWEROFF_STATE:
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ctrl_info(ctrl, "Slot(%s): Already in powering off state\n",
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@ -583,6 +583,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
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irqreturn_t ret;
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u32 events;
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ctrl->ist_running = true;
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pci_config_pm_runtime_get(pdev);
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/* rerun pciehp_isr() if the port was inaccessible on interrupt */
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@ -629,6 +630,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
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up_read(&ctrl->reset_lock);
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pci_config_pm_runtime_put(pdev);
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ctrl->ist_running = false;
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wake_up(&ctrl->requester);
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return IRQ_HANDLED;
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}
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