The VMObject class now manages its own instance list (it was previously
a member of MemoryManager.) Removal from the list is done safely on the
last unref(), closing a race window in the previous implementation.
Note that VMObject::all_instances() now has its own lock instead of
using the global MM lock.
Use a StringBuilder to generate a temporary string buffer with the
slave PTY names. (This works because StringBuilder has 128 bytes of
inline stack capacity before it does any heap allocations.)
This simplifies the DevPtsFS implementation somewhat, as it no longer
requires SlavePTY to register itself with it, since it can now simply
use the list of SlavePTY instances.
This class implements the emerging "ref-counted object that participates
in a lock-protected list that requires safe removal on unref()" pattern
as a base class that can be inherited in place of RefCounted<T>.
Make File inherit from RefCountedBase and provide a custom unref()
implementation. This will allow subclasses that participate in lists to
remove themselves in a safe way when being destroyed.
This patch adds a (spinlock-protected) custody cache. It's a simple
intrusive list containing all currently live custody objects.
This allows us to re-use existing custodies instead of creating them
again and again.
This gives a pretty decent performance improvement on "find /" :^)
We don't need to create a new string from a number in order to compare
an existing string to that number. Converting the existing string to a
number is much cheaper, since it does not require any heap allocations.
Ran into this while profiling "find /" :^)
There's no need for generated files in SysFS to tell you their precise
file size when you stat() them.
I noticed when profiling "find /" that we were spending a chunk of time
generating and throwing away SysFS content just so we could tell you
exactly how large it would be. :^)
Previously when trying to debug the system's routing, the ARP
information would clutter the output and make it difficult to focus on
the routing decisions. It would be better to specify these
debug messages under ARP_DEBUG.
This makes for nicer handling of errors compared to checking whether a
RefPtr is null. Additionally, this will give way to return different
types of errors in the future.
This patch does three things:
- Convert the global thread list from a HashMap to an IntrusiveList
- Combine the thread list and its lock into a SpinLockProtectedValue
- Customize Thread::unref() so it locks the list while unreffing
This closes the same race window for Thread as @sin-ack's recent changes
did for Process.
Note that the HashMap->IntrusiveList conversion means that we lose O(1)
lookups, but the majority of clients of this list are doing traversal,
not lookup. Once we have an intrusive hashing solution, we should port
this to use that, but for now, this gets rid of heap allocations during
a sensitive time.
We are not using this for anything and it's just been sitting there
gathering dust for well over a year, so let's stop carrying all this
complexity around for no good reason.
This patch replaces the remaining users of this API with the new
try_copy_kstring_from_user() instead. Note that we still convert to a
String for continued processing, and I've added FIXME about continuing
work on using KString all the way.
This makes the following scenario impossible with an SMP setup:
1) CPU A enters unref() and decrements the link count to 0.
2) CPU B sees the process in the process list and ref()s it.
3) CPU A removes the process from the list and continues destructing.
4) CPU B is now holding a destructed Process object.
By holding the process list lock before doing anything with it, we
ensure that other CPUs can't find this process in the middle of it being
destructed.
This allows us to 1) let go of the Process when an inode is ref'ing for
ProcFSExposedComponent related reasons, and 2) change our ref/unref
implementation.
A hub can technically have up to 255 ports, given that bNbrPorts is a
u8 and the DeviceRemovable field is a VLA to support up to 255 ports.
Source: USB 2.0 Specification Section 11.23.2.1
That means this enum is not going to scale well in terms of size.
Replacing it with a raw u8 allows me to remove the two port assumption
and a cast.
Previously it would create a contiguous AVMO manually and pass it to
MM. This uses supervisor pages that quickly run out as they never get
returned and crash the system.
Instead, use allocate_kernel_region as we're only allocating a page so
it will be contiguous and will be returned when destroyed.
A potentially better solution would be to use a pool of transfers to
avoid all the allocations. This just prevents the system from crashing
within ~5 seconds from the continuous hub polling.
