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Kernel/PCI: Don't hold spinlocks when doing fast device enumeration
Instead, hold the lock while we copy the contents to a stack-based Vector then iterate on it without any locking. Because we rely on heap allocations, we need to propagate errors back in case of OOM condition, therefore, both PCI::enumerate API function and PCI::Access::add_host_controller_and_enumerate_attached_devices use now a ErrorOr<void> return value to propagate errors. OOM Error can only occur when enumerating the m_device_identifiers vector under a spinlock and trying to expand the temporary Vector which will be used locklessly to actually iterate over the PCI::DeviceIdentifiers objects.
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14 changed files with 69 additions and 42 deletions
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@ -117,20 +117,36 @@ UNMAP_AFTER_INIT bool Access::initialize_for_one_pci_domain()
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return true;
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}
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void Access::add_host_controller_and_enumerate_attached_devices(NonnullOwnPtr<HostController> controller, Function<void(DeviceIdentifier const&)> callback)
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ErrorOr<void> Access::add_host_controller_and_enumerate_attached_devices(NonnullOwnPtr<HostController> controller, Function<void(DeviceIdentifier const&)> callback)
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{
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SpinlockLocker locker(m_access_lock);
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SpinlockLocker scan_locker(m_scan_lock);
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auto domain_number = controller->domain_number();
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// Note: We hold the spinlocks for a moment just to ensure we append the
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// device identifiers safely. Afterwards, enumeration goes lockless to allow
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// IRQs to be fired if necessary.
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Vector<DeviceIdentifier> device_identifiers_behind_host_controller;
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{
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SpinlockLocker locker(m_access_lock);
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SpinlockLocker scan_locker(m_scan_lock);
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auto domain_number = controller->domain_number();
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VERIFY(!m_host_controllers.contains(domain_number));
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// Note: We need to register the new controller as soon as possible, and
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// definitely before enumerating devices behing that.
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m_host_controllers.set(domain_number, move(controller));
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m_host_controllers.get(domain_number).value()->enumerate_attached_devices([&](DeviceIdentifier const& device_identifier) -> void {
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m_device_identifiers.append(device_identifier);
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VERIFY(!m_host_controllers.contains(domain_number));
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// Note: We need to register the new controller as soon as possible, and
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// definitely before enumerating devices behing that.
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m_host_controllers.set(domain_number, move(controller));
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ErrorOr<void> expansion_result;
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m_host_controllers.get(domain_number).value()->enumerate_attached_devices([&](DeviceIdentifier const& device_identifier) -> void {
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m_device_identifiers.append(device_identifier);
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auto result = device_identifiers_behind_host_controller.try_append(device_identifier);
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if (result.is_error())
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expansion_result = result;
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});
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if (expansion_result.is_error())
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return expansion_result;
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}
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for (auto const& device_identifier : device_identifiers_behind_host_controller) {
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callback(device_identifier);
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});
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}
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return {};
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}
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UNMAP_AFTER_INIT void Access::add_host_controller(NonnullOwnPtr<HostController> controller)
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@ -156,13 +172,20 @@ UNMAP_AFTER_INIT void Access::rescan_hardware()
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}
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}
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void Access::fast_enumerate(Function<void(DeviceIdentifier const&)>& callback) const
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ErrorOr<void> Access::fast_enumerate(Function<void(DeviceIdentifier const&)>& callback) const
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{
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SpinlockLocker locker(m_access_lock);
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VERIFY(!m_device_identifiers.is_empty());
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for (auto const& device_identifier : m_device_identifiers) {
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// Note: We hold the m_access_lock for a brief moment just to ensure we get
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// a complete Vector in case someone wants to mutate it.
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Vector<DeviceIdentifier> device_identifiers;
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{
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SpinlockLocker locker(m_access_lock);
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VERIFY(!m_device_identifiers.is_empty());
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TRY(device_identifiers.try_extend(m_device_identifiers));
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}
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for (auto const& device_identifier : device_identifiers) {
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callback(device_identifier);
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}
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return {};
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}
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DeviceIdentifier Access::get_device_identifier(Address address) const
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