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, 2 deletions

diff --git a/Kernel/Bus/PCI/Access.h b/Kernel/Bus/PCI/Access.h
index 8444b80c18..fa1dc16fb2 100644
--- a/Kernel/Bus/PCI/Access.h
+++ b/Kernel/Bus/PCI/Access.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Bitmap.h>
+#include <AK/Try.h>
 #include <AK/Vector.h>
 #include <Kernel/Bus/PCI/Controller/HostController.h>
 #include <Kernel/Bus/PCI/Definitions.h>
@@ -21,7 +22,7 @@ public:
     static bool initialize_for_multiple_pci_domains(PhysicalAddress mcfg_table);
     static bool initialize_for_one_pci_domain();
 
-    void fast_enumerate(Function<void(DeviceIdentifier const&)>&) const;
+    ErrorOr<void> fast_enumerate(Function<void(DeviceIdentifier const&)>&) const;
     void rescan_hardware();
 
     static Access& the();
@@ -39,7 +40,7 @@ public:
     Spinlock const& scan_lock() const { return m_scan_lock; }
     RecursiveSpinlock const& access_lock() const { return m_access_lock; }
 
-    void add_host_controller_and_enumerate_attached_devices(NonnullOwnPtr<HostController>, Function<void(DeviceIdentifier const&)> callback);
+    ErrorOr<void> add_host_controller_and_enumerate_attached_devices(NonnullOwnPtr<HostController>, Function<void(DeviceIdentifier const&)> callback);
 
 private:
     u8 read8_field(Address address, RegisterOffset field);