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Kernel/PCI: Don't hold spinlocks when doing fast device enumeration

Browse source 
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.
This commit is contained in:
Liav A 2022-02-04 19:48:13 +02:00 • committed by Andreas Kling
parent c0ed656c94
commit 3fb289e27d
14 changed files with 69 additions and 42 deletions
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53
Kernel/Bus/PCI/Access.cpp
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@ -117,20 +117,36 @@ UNMAP_AFTER_INIT bool Access::initialize_for_one_pci_domain()
return true;
}
void Access::add_host_controller_and_enumerate_attached_devices(NonnullOwnPtr<HostController> controller, Function<void(DeviceIdentifier const&)> callback)
ErrorOr<void> Access::add_host_controller_and_enumerate_attached_devices(NonnullOwnPtr<HostController> controller, Function<void(DeviceIdentifier const&)> callback)
{
SpinlockLocker locker(m_access_lock);
SpinlockLocker scan_locker(m_scan_lock);
auto domain_number = controller->domain_number();
// Note: We hold the spinlocks for a moment just to ensure we append the
// device identifiers safely. Afterwards, enumeration goes lockless to allow
// IRQs to be fired if necessary.
Vector<DeviceIdentifier> device_identifiers_behind_host_controller;
{
SpinlockLocker locker(m_access_lock);
SpinlockLocker scan_locker(m_scan_lock);
auto domain_number = controller->domain_number();
VERIFY(!m_host_controllers.contains(domain_number));
// Note: We need to register the new controller as soon as possible, and
// definitely before enumerating devices behing that.
m_host_controllers.set(domain_number, move(controller));
m_host_controllers.get(domain_number).value()->enumerate_attached_devices([&](DeviceIdentifier const& device_identifier) -> void {
m_device_identifiers.append(device_identifier);
VERIFY(!m_host_controllers.contains(domain_number));
// Note: We need to register the new controller as soon as possible, and
// definitely before enumerating devices behing that.
m_host_controllers.set(domain_number, move(controller));
ErrorOr<void> expansion_result;
m_host_controllers.get(domain_number).value()->enumerate_attached_devices([&](DeviceIdentifier const& device_identifier) -> void {
m_device_identifiers.append(device_identifier);
auto result = device_identifiers_behind_host_controller.try_append(device_identifier);
if (result.is_error())
expansion_result = result;
});
if (expansion_result.is_error())
return expansion_result;
}
for (auto const& device_identifier : device_identifiers_behind_host_controller) {
callback(device_identifier);
});
}
return {};
}
UNMAP_AFTER_INIT void Access::add_host_controller(NonnullOwnPtr<HostController> controller)
@ -156,13 +172,20 @@ UNMAP_AFTER_INIT void Access::rescan_hardware()
}
}
void Access::fast_enumerate(Function<void(DeviceIdentifier const&)>& callback) const
ErrorOr<void> Access::fast_enumerate(Function<void(DeviceIdentifier const&)>& callback) const
{
SpinlockLocker locker(m_access_lock);
VERIFY(!m_device_identifiers.is_empty());
for (auto const& device_identifier : m_device_identifiers) {
// Note: We hold the m_access_lock for a brief moment just to ensure we get
// a complete Vector in case someone wants to mutate it.
Vector<DeviceIdentifier> device_identifiers;
{
SpinlockLocker locker(m_access_lock);
VERIFY(!m_device_identifiers.is_empty());
TRY(device_identifiers.try_extend(m_device_identifiers));
}
for (auto const& device_identifier : device_identifiers) {
callback(device_identifier);
}
return {};
}
DeviceIdentifier Access::get_device_identifier(Address address) const