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.

1 files changed, 3 insertions, 1 deletions

diff --git a/Kernel/Bus/PCI/API.h b/Kernel/Bus/PCI/API.h
index 198e55e1d9..6c95db9aa8 100644
--- a/Kernel/Bus/PCI/API.h
+++ b/Kernel/Bus/PCI/API.h
@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <AK/Error.h>
+#include <AK/Try.h>
 #include <Kernel/Bus/PCI/Definitions.h>
 
 namespace Kernel::PCI {
@@ -19,7 +21,7 @@ u32 read32(Address address, PCI::RegisterOffset field);
 
 HardwareID get_hardware_id(PCI::Address);
 bool is_io_space_enabled(Address);
-void enumerate(Function<void(DeviceIdentifier const&)> callback);
+ErrorOr<void> enumerate(Function<void(DeviceIdentifier const&)> callback);
 void enable_interrupt_line(Address);
 void disable_interrupt_line(Address);
 void raw_access(Address, u32, size_t, u32);