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That's what this class really is; in fact that's what the first line of
the comment says it is.
This commit does not rename the main files, since those will contain
other time-related classes in a little bit.
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Had to wrap Process::m_pg in a SpinlockProtected for this to be safe.
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These were stored in a bunch of places. The main one that's a bit iffy
is the Mutex::m_holder one, which I'm going to simplify in a subsequent
commit.
In Plan9FS and WorkQueue, we can't make the NNRPs const due to
initialization order problems. That's probably doable with further
cleanup, but left as an exercise for our future selves.
Before starting this, I expected the thread blockers to be a problem,
but as it turns out they were super straightforward (for once!) as they
don't mutate the thread after initiating a block, so they can just use
simple const-ified NNRPs.
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The only persistent one of these was Thread::m_process and that never
changes after initialization. Make it const to enforce this and switch
everything over to RefPtr & NonnullRefPtr.
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The main place where this is a little iffy is in RAMFS where inodes
have a LockWeakPtr to their parent inode. I've left that as a
LockWeakPtr for now.
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This patch switches away from {Nonnull,}LockRefPtr to the non-locking
smart pointers throughout the kernel.
I've looked at the handful of places where these were being persisted
and I don't see any race situations.
Note that the process file descriptor table (Process::m_fds) was already
guarded via MutexProtected.
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This replaces manually grabbing the thread's main lock.
This lets us remove the `get_thread_name` and `set_thread_name` syscalls
from the big lock. :^)
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Various places in the kernel were manually checking the cs register for
x86_64, however to share this with aarch64 a function in RegisterState
is added, and the call-sites are updated. While we're here the
PreviousMode enum is renamed to ExecutionMode.
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Make Userland and Tests users just include signal.h, and move Kernel
users to the new API file.
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Functions defined inside class bodies (including static functions)
are implicitly inline, no need to type it out.
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This step would ideally not have been necessary (increases amount of
refactoring and templates necessary, which in turn increases build
times), but it gives us a couple of nice properties:
- SpinlockProtected inside Singleton (a very common combination) can now
obtain any lock rank just via the template parameter. It was not
previously possible to do this with SingletonInstanceCreator magic.
- SpinlockProtected's lock rank is now mandatory; this is the majority
of cases and allows us to see where we're still missing proper ranks.
- The type already informs us what lock rank a lock has, which aids code
readability and (possibly, if gdb cooperates) lock mismatch debugging.
- The rank of a lock can no longer be dynamic, which is not something we
wanted in the first place (or made use of). Locks randomly changing
their rank sounds like a disaster waiting to happen.
- In some places, we might be able to statically check that locks are
taken in the right order (with the right lock rank checking
implementation) as rank information is fully statically known.
This refactoring even more exposes the fact that Mutex has no lock rank
capabilites, which is not fixed here.
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These are architecture-specific anyway, so they belong in the Arch
directory. This commit also adds ThreadRegisters::set_initial_state to
factor out the logic in Thread.cpp.
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Joining dead threads is allowed for two main reasons:
- Thread join behavior should not be racy when a thread is joined and
exiting at roughly the same time. This is common behavior when threads
are given a signal to end (meaning they are going to exit ASAP) and
then joined.
- POSIX requires that exited threads are joinable (at least, there is no
language in the specification forbidding it).
The behavior is still well-defined; e.g. it doesn't allow a dead
detached thread to be joined or a thread to be joined more than once.
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The priority range was changed several years ago, but the
userland-reported limits were just forgotten :skeleyak:. Move the thread
priority constants into an API header so that userland can use it
properly.
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This commit updates the lock function from Spinlock and
RecursiveSpinlock to return the InterruptsState of the processor,
instead of the processor flags. The unlock functions would only look at
the interrupt flag of the processor flags, so we now use the
InterruptsState enum to clarify the intent, and such that we can use the
same Spinlock code for the aarch64 build.
To not break the build, all the call sites are updated aswell.
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Until now, our kernel has reimplemented a number of AK classes to
provide automatic internal locking:
- RefPtr
- NonnullRefPtr
- WeakPtr
- Weakable
This patch renames the Kernel classes so that they can coexist with
the original AK classes:
- RefPtr => LockRefPtr
- NonnullRefPtr => NonnullLockRefPtr
- WeakPtr => LockWeakPtr
- Weakable => LockWeakable
The goal here is to eventually get rid of the Lock* classes in favor of
using external locking.
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All users which relied on the default constructor use a None lock rank
for now. This will make it easier to in the future remove LockRank and
actually annotate the ranks by searching for None.
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We can use simple atomic variables with relaxed ordering for this,
and avoid locking altogether.
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This knocks 70 MiB off our idle footprint, (from 350 MiB to 280 MiB.)
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As required by Dr. Posix.
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When updating the signal mask, there is a small frame where we might set
up the receiving process for handing the signal and therefore remove
that signal from the list of pending signals before SignalBlocker has a
chance to block. In turn, this might cause SignalBlocker to never notice
that the signal arrives and it will never unblock once blocked.
Track the currently handled signal separately and include it when
determining if SignalBlocker should be unblocking.
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This makes the main thread stack size the same as the default stack
size when creating new threads.
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When we lock a mutex, eventually `Thread::block` is invoked which could
in turn invoke `Process::big_lock().restore_exclusive_lock()`. This
would then try to add the current thread to a different blocked thread
list then the one in use for the original mutex being locked, and
because it's an intrusive list, the thread is removed from its original
list during the `.append()`. When the original mutex eventually
unblocks, we no longer have the thread in the intrusive blocked threads
list and we panic.
Solve this by making the big lock mutex special and giving it its own
blocked thread list. Because the process big lock is temporary and is
being actively removed from e.g. syscalls, it's a matter of time before
we can also remove the fix introduced by this commit.
Fixes issue #9401.
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There's no reason to fill in any of these fields if SA_SIGINFO is not
given, as the signal handler won't be reading from them at all.
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POSIX requires that sigaction() and friends set a _process-wide_ signal
handler, so move signal handlers and flags inside Process.
This also fixes a "pid/tid confusion" FIXME, as we can now send the
signal to the process and let that decide which thread should get the
signal (which is the thread with tid==pid, but that's now the Process's
problem).
Note that each thread still retains its signal mask, as that is local to
each thread.
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It's more accurate to say that we're blocking on a mutex, rather than
blocking on a lock. The previous terminology made sense when this code
was using something called Kernel::Lock, but since it was renamed to
Kernel::Mutex, this updates brings the language back in sync.
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It was annoyingly hard to spot these when we were using them with
different amounts of qualification everywhere.
This patch uses Thread::State::Foo everywhere instead of Thread::Foo
or just Foo.
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Signal dispatch is already taken care of elsewhere, so there appears to
be no need for the hack in enter_current().
This also allows us to remove the Thread::m_in_block flag, simplifying
thread blocking logic somewhat.
Verified with the original repro for #4336 which this was meant to fix.
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...and deal with the fallout by adding missing includes everywhere.
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This function is large and unwieldy and forces Thread.h to #include
a bunch of things. The only reason it was in the header is because we
need to instantiate a blocker based on the templated BlockerType.
We actually keep block<BlockerType>() in the header, but move the
bulk of the function body out of line into Thread::block_impl().
To preserve destructor ordering, we add Blocker::finalize() which is
called where we'd previously destroy the Blocker.
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For "destructive" disallowance of allocations throughout the system,
Thread gains a member that controls whether allocations are currently
allowed or not. kmalloc checks this member on both allocations and
deallocations (with the exception of early boot) and panics the kernel
if allocations are disabled. This will allow for critical sections that
can't be allowed to allocate to fail-fast, making for easier debugging.
PS: My first proper Kernel commit :^)
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This OwnPtr is always non-null, so let's enforce it statically.
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This change adds a thread member variable to track if we have a pending
promise violation on a kernel thread. This ensures that all code
properly propagates promise violations up to the syscall handler.
Suggested-by: Andreas Kling <kling@serenityos.org>
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This will allow us to support Mutex Protected lists like the custodies
list as well.
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Instead, wait until we transition back to userspace. This stops
userspace from being able to suspend a thread indefinitely while it's
running in kernelspace (potentially holding some blocking mutex.)
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This includes a new Thread::Blocker called SignalBlocker which blocks
until a signal of a matching type is pending. The current Blocker
implementation in the Kernel is very complicated, but cleaning it up is
a different yak for a different day.
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As required by posix. Also rename Thread::clear_signals to
Thread::reset_signals_for_exec since it doesn't actually clear any
pending signals, but rather does execve related signal book-keeping.
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This matches the behaviour of the other *nixs and allows processes to
try and recover from such signals in userland.
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