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Kernel: Avoid double-locking devices when trying to acquire them

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Previously, you'd occasionally see this sort of construct (simplified):
```
return FooDevice::all_instances().with([&](auto& list) {
    for (auto& device : list) {
        if (/* search condition */)
            continue;
        return do_something_that_reacquires(device.index());
    }
    return ENOENT;
});
```

This would only work if the relevant `all_instances()` used a recursive
spinlock, since reacquiring the device would lock that again.

To get around this, a new helper has been added in `Device` through
which devices can be accessed whilst locking the device list, removing
the need to loop through the device type's `all_instances()`.
This commit is contained in:
implicitfield
2025-05-16 14:12:16 +03:00
committed by Sönke Holz
parent d3a314f5cd
commit 6a4ceb6bf2
12 changed files with 74 additions and 59 deletions
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30
Kernel/FileSystem/DevPtsFS/FileSystem.cpp
View File

@@ -6,6 +6,7 @@
*/
#include <Kernel/API/DeviceFileTypes.h>
#include <Kernel/API/MajorNumberAllocation.h>
#include <Kernel/Devices/Device.h>
#include <Kernel/Devices/TTY/SlavePTY.h>
#include <Kernel/FileSystem/DevPtsFS/FileSystem.h>
@@ -61,18 +62,31 @@ ErrorOr<NonnullRefPtr<Inode>> DevPtsFS::get_inode(InodeIdentifier inode_id) cons
return *m_root_inode;
unsigned pty_index = inode_index_to_pty_index(inode_id.index());
auto device = Device::acquire_by_type_and_major_minor_numbers(DeviceNodeType::Character, 201, pty_index);
VERIFY(device);
auto& pts_device = static_cast<SlavePTY&>(*device);
auto inode = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) DevPtsFSInode(const_cast<DevPtsFS&>(*this), inode_id.index(), pts_device)));
UserID pty_uid;
GroupID pty_gid;
LockRefPtr<SlavePTY> device;
Device::run_by_type_and_major_minor_numbers(DeviceNodeType::Character, to_underlying(MajorAllocation::CharacterDeviceFamily::SlavePTY), pty_index, [&](RefPtr<Device> found_device) {
if (!found_device)
return;
auto& pty = static_cast<SlavePTY&>(*found_device);
pty_uid = pty.uid();
pty_gid = pty.gid();
device = pty;
});
if (!device)
return ENOENT;
auto inode = TRY(adopt_nonnull_ref_or_enomem(new (nothrow) DevPtsFSInode(const_cast<DevPtsFS&>(*this), inode_id.index(), device)));
inode->m_metadata.inode = inode_id;
inode->m_metadata.size = 0;
inode->m_metadata.uid = pts_device.uid();
inode->m_metadata.gid = pts_device.gid();
inode->m_metadata.uid = pty_uid;
inode->m_metadata.gid = pty_gid;
inode->m_metadata.mode = 0020600;
inode->m_metadata.major_device = device->major();
inode->m_metadata.minor_device = device->minor();
inode->m_metadata.major_device = to_underlying(MajorAllocation::CharacterDeviceFamily::SlavePTY);
inode->m_metadata.minor_device = pty_index;
inode->m_metadata.mtime = TimeManagement::boot_time();
return inode;
}