This switches tracking CPU usage to more accurately measure time in
user and kernel land using either the TSC or another time source.
This will also come in handy when implementing a tickless kernel mode.
The compiler will use these to allocate objects that have alignment
requirements greater than that of our normal `operator new` (4/8 byte
aligned).
This means we can now use smart pointers for over-aligned types.
Fixes a FIXME.
Thread::yield_and_release_relock_big_lock releases the big lock, yields
and then relocks the big lock.
Thread::yield_assuming_not_holding_big_lock yields assuming the big
lock is not being held.
This reverts commit 3c3a1726df.
We cannot blindly kill threads just because they're not executing in a
system call. Being blocked (including in a page fault) needs proper
unblocking and potentially kernel stack cleanup before we can mark a
thread as Dying.
Fixes#8691
This enables the Lock class to block a thread even while the thread is
working on a BlockCondition. A thread can still only be either blocked
by a Lock or a BlockCondition.
This also establishes a linked list of threads that are blocked by a
Lock and unblocking directly unlocks threads and wakes them directly.
This was an old SerenityOS-specific syscall for donating the remainder
of the calling thread's time-slice to another thread within the same
process.
Now that Threading::Lock uses a pthread_mutex_t internally, we no
longer need this syscall, which allows us to get rid of a surprising
amount of unnecessary scheduler logic. :^)
The new ProcFS design consists of two main parts:
1. The representative ProcFS class, which is derived from the FS class.
The ProcFS and its inodes are much more lean - merely 3 classes to
represent the common type of inodes - regular files, symbolic links and
directories. They're backed by a ProcFSExposedComponent object, which
is responsible for the functional operation behind the scenes.
2. The backend of the ProcFS - the ProcFSComponentsRegistrar class
and all derived classes from the ProcFSExposedComponent class. These
together form the entire backend and handle all the functions you can
expect from the ProcFS.
The ProcFSExposedComponent derived classes split to 3 types in the
manner of lifetime in the kernel:
1. Persistent objects - this category includes all basic objects, like
the root folder, /proc/bus folder, main blob files in the root folders,
etc. These objects are persistent and cannot die ever.
2. Semi-persistent objects - this category includes all PID folders,
and subdirectories to the PID folders. It also includes exposed objects
like the unveil JSON'ed blob. These object are persistent as long as the
the responsible process they represent is still alive.
3. Dynamic objects - this category includes files in the subdirectories
of a PID folder, like /proc/PID/fd/* or /proc/PID/stacks/*. Essentially,
these objects are always created dynamically and when no longer in need
after being used, they're deallocated.
Nevertheless, the new allocated backend objects and inodes try to use
the same InodeIndex if possible - this might change only when a thread
dies and a new thread is born with a new thread stack, or when a file
descriptor is closed and a new one within the same file descriptor
number is opened. This is needed to actually be able to do something
useful with these objects.
The new design assures that many ProcFS instances can be used at once,
with one backend for usage for all instances.
Steps to reproduce:
$ cat loop.c
int main() { for (;;); }
$ gcc -o loop loop.c
$ ./loop
Terminating this process wasn't previously possible because we only
checked whether the thread should be terminated on syscall exit.
There were a few cases where we could end up logging profiling events
before or after the associated process or thread exists in the profile:
After enabling profiling we might end up with CPU samples before we
had a chance to synthesize process/thread creation events.
After a thread exits we would still log associated kmalloc/kfree
events. Instead we now just ignore those events.
Hook the kernel page fault handler and capture page fault events when
the fault has a current thread attached in TLS. We capture the eip and
ebp so we can unwind the stack and locate which pieces of code are
generating the most page faults.
Co-authored-by: Gunnar Beutner <gbeutner@serenityos.org>
By constraining two implementations, the compiler will select the best
fitting one. All this will require is duplicating the implementation and
simplifying for the `void` case.
This constraining also informs both the caller and compiler by passing
the callback parameter types as part of the constraint
(e.g.: `IterationFunction<int>`).
Some `for_each` functions in LibELF only take functions which return
`void`. This is a minimal correctness check, as it removes one way for a
function to incompletely do something.
There seems to be a possible idiom where inside a lambda, a `return;` is
the same as `continue;` in a for-loop.
FileDescriptionBlocker::m_should_block was shadowing the parent's
FileBlocker::m_should_block variable, which would cause should_block()
to return the wrong value.
Found by @gunnarbeutner
This solves a problem where checking whether a thread is an idle
thread may require iterating all processors if it is not the idle
thread of the current processor.
The previous `LOCKER(..)` instrumentation only covered some of the
cases where a lock is actually acquired. By utilizing the new
`AK::SourceLocation` functionality we can now reliably instrument
all calls to lock automatically.
Other changes:
- Tweak the message in `Thread::finalize()` which dumps leaked lock
so it's more readable and includes the function information that is
now available.
- Make the `LOCKER(..)` define a no-op, it will be cleaned up in a
follow up change.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This adds PT_PEEKDEBUG and PT_POKEDEBUG to allow for reading/writing
the debug registers, and updates the Kernel's debug handler to read the
new information from the debug status register.
This should allow creating intrusive lists that have smart pointers,
while remaining free (compared to the impl before this commit) when
holding raw pointers :^)
As a sidenote, this also adds a `RawPtr<T>` type, which is just
equivalent to `T*`.
Note that this does not actually use such functionality, but is only
expected to pave the way for #6369, to replace NonnullRefPtrVector<T>
with intrusive lists.
As it is with zero-cost things, this makes the interface a bit less nice
by requiring the type name of what an `IntrusiveListNode` holds (and
optionally its container, if not RawPtr), and also requiring the type of
the container (normally `RawPtr`) on the `IntrusiveList` instance.
Alot of code is shared between i386/i686/x86 and x86_64
and a lot probably will be used for compatability modes.
So we start by moving the headers into one Directory.
We will probalby be able to move some cpp files aswell.
Switch to using type-safe bitwise operators for the BlockFlags class,
this cleans up a lot of boilerplate casts which are necessary when the
enum is declared as `enum class`.
Dynamic Vector allocations in sys$select() were showing up in the
full-system profile and since there will never be more than FD_SETSIZE
file descriptors to worry about, we can confidently add enough inline
capacity to this Vector that it never has to kmalloc.
To compensate for the increased stack usage, reduce the size of the
FDInfo struct while we're here. :^)
This commit is very invasive, because Thread likes to take a pointer and write
to it. This means that translating between timespec/timeval/Time would have been
more difficult than just changing everything that hands a raw pointer to Thread,
in bulk.
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
The `default_signal_action(u8 signal)` function already has the
full mapping. The only caveat being that now we need to make
sure the thread constructor and clear_signals() method do the work
of resetting the m_signal_action_data array, instead or relying on
the previous logic in set_default_signal_dispositions.
In the majority of cases we want to force callers to observe the
result of a blocking operation as it's not grantee to succeed as
they expect. Mark BlockResult as [[nodiscard]] to force any callers
to observe the result of the blocking operation.
Not sure why this was 4 MiB in the first place, but that's a lot of
memory to reserve for each thread when we're running with 512 MiB
total in the default testing setup. :^)
Wrap thread creation in a Thread::try_create() helper that first
allocates a kernel stack region. If that allocation fails, we propagate
an ENOMEM error to the caller.
This avoids the situation where a thread is half-constructed, without a
valid kernel stack, and avoids having to do messy cleanup in that case.
There's no need for this to be generic and support running from an
arbitrary thread context. Perf events are always generated from within
the thread being profiled, so take advantage of that to simplify the
code. Also use Vector capacity to avoid heap allocations.
This allows us to get rid of the thread lists in SchedulerData.
Also, instead of iterating over all threads to find a thread by id,
just use a lookup table. In the rare case of having to iterate over
all threads, just iterate the lookup table.
This broke with the change that gave each process a list of its own
threads. Since threads are removed slightly earlier from that list
during process teardown, we're not able to use it for generating
coredump backtraces. Fortunately we have the "threads for coredump"
list for just this purpose. :^)
Rather than walking all Thread instances and putting them into
a vector to be sorted by priority, queue them into priority sorted
linked lists as soon as they become ready to be executed.
Change Thread::current to be a static function and read using the fs
register, which eliminates a window between Processor::current()
returning and calling a function on it, which can trigger preemption
and a move to a different processor, which then causes operating
on the wrong object.
We also need to store m_in_critical in the Thread upon switching,
and we need to restore it. This solves a problem where threads
moving between different processors could end up with an unexpected
value.
This allows us to determine what the previous mode (user or kernel)
was, e.g. in the timer interrupt. This is used e.g. to determine
whether a signal handler should be set up.
Fixes#5096
This was done with the help of several scripts, I dump them here to
easily find them later:
awk '/#ifdef/ { print "#cmakedefine01 "$2 }' AK/Debug.h.in
for debug_macro in $(awk '/#ifdef/ { print $2 }' AK/Debug.h.in)
do
find . \( -name '*.cpp' -o -name '*.h' -o -name '*.in' \) -not -path './Toolchain/*' -not -path './Build/*' -exec sed -i -E 's/#ifdef '$debug_macro'/#if '$debug_macro'/' {} \;
done
# Remember to remove WRAPPER_GERNERATOR_DEBUG from the list.
awk '/#cmake/ { print "set("$2" ON)" }' AK/Debug.h.in
It was possible to signal a process while it was paging in an inode
backed VM object. This would cause the inode read to EINTR, and the
page fault handler would assert.
Solve this by simply not unblocking threads due to signals if they are
currently busy handling a page fault. This is probably not the best way
to solve this issue, so I've added a FIXME to that effect.
..and allow implicit creation of KResult and KResultOr from ErrnoCode.
This means that kernel functions that return those types can finally
do "return EINVAL;" and it will just work.
There's a handful of functions that still deal with signed integers
that should be converted to return KResults.
This adds support for FUTEX_WAKE_OP, FUTEX_WAIT_BITSET, FUTEX_WAKE_BITSET,
FUTEX_REQUEUE, and FUTEX_CMP_REQUEUE, as well well as global and private
futex and absolute/relative timeouts against the appropriate clock. This
also changes the implementation so that kernel resources are only used when
a thread is blocked on a futex.
Global futexes are implemented as offsets in VMObjects, so that different
processes can share a futex against the same VMObject despite potentially
being mapped at different virtual addresses.
The priority boosting mechanism has been broken for a very long time.
Let's remove it from the codebase and we can bring it back the day
someone feels like implementing it in a working way. :^)
Problem:
- Many constructors are defined as `{}` rather than using the ` =
default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
instead of requiring the caller to default construct. This violates
the C++ Core Guidelines suggestion to declare single-argument
constructors explicit
(https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).
Solution:
- Change default constructors to use the compiler-provided default
constructor.
- Remove implicit conversion operators from `nullptr_t` and change
usage to enforce type consistency without conversion.
BlockCondition::unblock should return true if it unblocked at
least one thread, not if iterating the blockers had been stopped.
This is a regression introduced by 49a76164c.
Fixes#4670
The unblock_all variant used to ASSERT if a blocker didn't unblock,
but it wasn't clear from the name that it would do that. Because
the BlockCondition already asserts that no blockers are left at
destruction time, it would still catch blockers that haven't been
unblocked for whatever reason.
Fixes#4496
If the allocation fails (e.g ENOMEM) we want to simply return an error
from sys$execve() and continue executing the current executable.
This patch also moves make_userspace_stack_for_main_thread() out of the
Thread class since it had nothing in particular to do with Thread.
This implements a number of changes related to time:
* If a HPET is present, it is now used only as a system timer, unless
the Local APIC timer is used (in which case the HPET timer will not
trigger any interrupts at all).
* If a HPET is present, the current time can now be as accurate as the
chip can be, independently from the system timer. We now query the
HPET main counter for the current time in CPU #0's system timer
interrupt, and use that as a base line. If a high precision time is
queried, that base line is used in combination with quering the HPET
timer directly, which should give a much more accurate time stamp at
the expense of more overhead. For faster time stamps, the more coarse
value based on the last interrupt will be returned. This also means
that any missed interrupts should not cause the time to drift.
* The default system interrupt rate is reduced to about 250 per second.
* Fix calculation of Thread CPU usage by using the amount of ticks they
used rather than the number of times a context switch happened.
* Implement CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE and use it
for most cases where precise timestamps are not needed.
We need to account for how many shared lock instances the current
thread owns, so that we can properly release such references when
yielding execution.
We also need to release the process lock when donating.
Since the process lock is using the Lock class, re-locking the process
lock may cause another call to Thread::block. This caused some problems
with multiple blockers attempting to be used at the same time. To solve
this problem, remember if the process lock was held, and if it was then
relock after we're done with the blockers, just before returning.
This prevents zombies created by multi-threaded applications and brings
our model back to closer to what other OSs do.
This also means that SIGSTOP needs to halt all threads, and SIGCONT needs
to resume those threads.
This is necessary because if a process changes the state to Stopped
or resumes from that state, a wait entry is created in the parent
process. So, if a child process does this before disown is called,
we need to clear those entries to avoid leaking references/zombies
that won't be cleaned up until the former parent exits.
This also should solve an even more unlikely corner case where another
thread is waiting on a pid that is being disowned by another thread.
Fix some problems with join blocks where the joining thread block
condition was added twice, which lead to a crash when trying to
unblock that condition a second time.
Deferred block condition evaluation by File objects were also not
properly keeping the File object alive, which lead to some random
crashes and corruption problems.
Other problems were caused by the fact that the Queued state didn't
handle signals/interruptions consistently. To solve these issues we
remove this state entirely, along with Thread::wait_on and change
the WaitQueue into a BlockCondition instead.
Also, deliver signals even if there isn't going to be a context switch
to another thread.
Fixes#4336 and #4330
This allows us to use blocking timeouts with either monotonic or
real time for all blockers. Which means that clock_nanosleep()
now also supports CLOCK_REALTIME.
Also, switch alarm() to use CLOCK_REALTIME as per specification.
We need to be able to guarantee that a timer won't be executing after
TimerQueue::cancel_timer returns. In the case of multiple processors
this means that we may need to wait while the timer handler finishes
execution on another core.
This also fixes a problem in Thread::block and Thread::wait_on where
theoretically the timer could execute after the function returned
and the Thread disappeared.
This changes the Thread::wait_on function to not enable interrupts
upon leaving, which caused some problems with page fault handlers
and in other situations. It may now be called from critical
sections, with interrupts enabled or disabled, and returns to the
same state.
This also requires some fixes to Lock. To aid debugging, a new
define LOCK_DEBUG is added that enables checking for Lock leaks
upon finalization of a Thread.
This makes the Scheduler a lot leaner by not having to evaluate
block conditions every time it is invoked. Instead evaluate them as
the states change, and unblock threads at that point.
This also implements some more waitid/waitpid/wait features and
behavior. For example, WUNTRACED and WNOWAIT are now supported. And
wait will now not return EINTR when SIGCHLD is delivered at the
same time.
This adds the ability to pass a pointer to kernel thread/process.
Also add the ability to use a closure as thread function, which
allows passing information to a kernel thread more easily.
Use the TimerQueue to expire blocking operations, which is one less thing
the Scheduler needs to check on every iteration.
Also, add a BlockTimeout class that will automatically handle relative or
absolute timeouts as well as overriding timeouts (e.g. socket timeouts)
more consistently.
Also, rework the TimerQueue class to be able to fire events from
any processor, which requires Timer to be RefCounted. Also allow
creating id-less timers for use by blocking operations.
The time returned by sys$clock_gettime() was not aligned with the delay
calculations in sys$clock_nanosleep(). This patch fixes that by taking
the system's ticks_per_second value into account in both functions.
This patch also removes the need for Thread::sleep_until() and uses
Thread::sleep() for both absolute and relative sleeps.
This was causing the nesalizer emulator port to sleep for a negative
amount of time at the end of each frame, making it run way too fast.
g_scheduler_lock cannot safely be acquired after Thread::m_lock
because another processor may already hold g_scheduler_lock and wait
for the same Thread::m_lock.
Similar to Process, we need to make Thread refcounted. This will solve
problems that will appear once we schedule threads on more than one
processor. This allows us to hold onto threads without necessarily
holding the scheduler lock for the entire duration.
The thread joining logic hadn't been updated to account for the subtle
differences introduced by software context switching. This fixes several
race conditions related to thread destruction and joining, as well as
finalization which did not properly account for detached state and the
fact that threads can be joined after termination as long as they're not
detached.
Fixes#3596
There are plenty of places in the kernel that aren't
checking if they actually got their allocation.
This fixes some of them, but definitely not all.
Fixes#3390Fixes#3391
Also, let's make find_one_free_page() return nullptr
if it doesn't get a free index. This stops the kernel
crashing when out of memory and allows memory purging
to take place again.
Fixes#3487
Since the CPU already does almost all necessary validation steps
for us, we don't really need to attempt to do this. Doing it
ourselves doesn't really work very reliably, because we'd have to
account for other processors modifying virtual memory, and we'd
have to account for e.g. pages not being able to be allocated
due to insufficient resources.
So change the copy_to/from_user (and associated helper functions)
to use the new safe_memcpy, which will return whether it succeeded
or not. The only manual validation step needed (which the CPU
can't perform for us) is making sure the pointers provided by user
mode aren't pointing to kernel mappings.
To make it easier to read/write from/to either kernel or user mode
data add the UserOrKernelBuffer helper class, which will internally
either use copy_from/to_user or directly memcpy, or pass the data
through directly using a temporary buffer on the stack.
Last but not least we need to keep syscall params trivial as we
need to copy them from/to user mode using copy_from/to_user.
I decided to modify MappedROM.h because all other entried in Forward.h
are also classes, and this is visually more pleasing.
Other than that, it just doesn't make any difference which way we resolve
the conflicts.
In c3d231616c we added the atomic variable
m_have_any_unmasked_pending_signals tracking the state of pending signals.
Add helper functions that automatically update this variable as needed.
We need to wait until a thread is fully set up and ready for running
before attempting to deliver a signal. Otherwise we may not have a
user stack yet.
Also, remove the Skip0SchedulerPasses and Skip1SchedulerPass thread
states that we don't really need anymore with software context switching.
Fixes the kernel crash reported in #3419
The SI prefixes "k", "M", "G" mean "10^3", "10^6", "10^9".
The IEC prefixes "Ki", "Mi", "Gi" mean "2^10", "2^20", "2^30".
Let's use the correct name, at least in code.
Only changes the name of the constants, no other behavior change.
We need to always return from Thread::wait_on, even when a thread
is being killed. This is necessary so that the kernel call stack
can clean up and release references held by it. Then, right before
transitioning back to user mode, we check if the thread is
supposed to die, and at that point change the thread state to
Dying to prevent further scheduling of this thread.
This addresses some possible resource leaks similar to #3073
This compiles, and contains exactly the same bugs as before.
The regex 'FIXME: PID/' should reveal all markers that I left behind, including:
- Incomplete conversion
- Issues or things that look fishy
- Actual bugs that will go wrong during runtime
If a thread is waiting but getting killed, we need to dequeue
the thread from the WaitQueue so that a potential wake before
finalization doesn't happen.
Allow passing in an optional timeout to Thread::block and move
the timeout check out of Thread::Blocker. This way all Blockers
implicitly support timeouts and don't need to implement it
themselves. Do however allow them to override timeouts (e.g.
for sockets).
We need to have a Thread lock to protect threading related
operations, such as Thread::m_blocker which is used in
Thread::block.
Also, if a Thread::Blocker indicates that it should be
unblocking immediately, don't actually block the Thread
and instead return immediately in Thread::block.
This fixes a regression introduced by the new software context
switching where the Kernel would not deliver a signal unless the
process is making system calls. This is because the TSS no longer
updates the CS value, so the scheduler never considered delivery
as the process always appeared to be in kernel mode. With software
context switching we can just set up the signal trampoline at
any time and when the processor returns back to user mode it'll
get executed. This should fix e.g. killing programs that are
stuck in some tight loop that doesn't make any system calls and
is only pre-empted by the timer interrupt.
Fixes#2958
By making the Process class RefCounted we don't really need
ProcessInspectionHandle anymore. This also fixes some race
conditions where a Process may be deleted while still being
used by ProcFS.
Also make sure to acquire the Process' lock when accessing
regions.
Last but not least, there's no reason why a thread can't be
scheduled while being inspected, though in practice it won't
happen anyway because the scheduler lock is held at the same
time.
Because Thread::sleep is an internal interface, it's easy to check that there
are only few callers: Process::sys$sleep, usleep, and nanosleep are happy
with this increased size, because now they support the entire range of their
arguments (assuming small-ish values for ticks_per_second()).
SyncTask doesn't care.
Note that the old behavior wasn't "cap out at 388 days", which would have been
reasonable. Instead, the code resulted in unsigned overflow, meaning that a
very long sleep would "on average" end after about 194 days, sometimes much
quicker.
We now have BlockResult::WokeNormally and BlockResult::NotBlocked,
both of which indicate no error. We can no longer just check for
BlockResult::WokeNormally and assume anything else must be an
interruption.
The AT_* entries are placed after the environment variables, so that
they can be found by iterating until the end of the envp array, and then
going even further beyond :^)
If WaitQueue::wake_all, WaitQueue::wake_one, or WaitQueue::wake_n
is called but nobody is currently waiting, we should remember that
fact and prevent someone from waiting after such a request. This
solves a race condition where the Finalizer thread is notified
to finalize a thread, but it is not (yet) waiting on this queue.
Fixes#2693
These changes solve a number of problems with the software
context swithcing:
* The scheduler lock really should be held throughout context switches
* Transitioning from the initial (idle) thread to another needs to
hold the scheduler lock
* Transitioning from a dying thread to another also needs to hold
the scheduler lock
* Dying threads cannot necessarily be finalized if they haven't
switched out of it yet, so flag them as active while a processor
is running it (the Running state may be switched to Dying while
it still is actually running)
The Lock class still permits no reason, but for everything else
require a reason to be passed to Thread::wait_on. This makes it
easier to diagnose why a Thread is in Queued state.
If we're trying to walk the stack for another thread, we can
no longer retreive the EBP register from Thread::m_tss. Instead,
we need to look at the top of the kernel stack, because all threads
not currently running were last in kernel mode. Context switches
now always trigger a brief switch to kernel mode, and Thread::m_tss
only is used to save ESP and EIP.
Fixes#2678
When delivering urgent signals to the current thread
we need to check if we should be unblocked, and if not
we need to yield to another process.
We also need to make sure that we suppress context switches
during Process::exec() so that we don't clobber the registers
that it sets up (eip mainly) by a context switch. To be able
to do that we add the concept of a critical section, which are
similar to Process::m_in_irq but different in that they can be
requested at any time. Calls to Scheduler::yield and
Scheduler::donate_to will return instantly without triggering
a context switch, but the processor will then asynchronously
trigger a context switch once the critical section is left.
pselect() is similar() to select(), but it takes its timeout
as timespec instead of as timeval, and it takes an additional
sigmask parameter.
Change the sys$select parameters to match pselect() and implement
select() in terms of pselect().
If these methods get inlined, the compiler is able to statically eliminate most
of the assertions. Alas, it doesn't realize this, and believes inlining them to
be too expensive. So give it a strong hint that it's not the case.
This *decreases* the kernel binary size.
This change plumbs a new optional timeout option to wait_on.
The timeout is enabled by enqueing a timer on the timer queue
while we are waiting. We can then see if we were woken up or
timed out by checking if we are still on the wait queue or not.
PT_SETTREGS sets the regsiters of the traced thread. It can only be
used when the tracee is stopped.
Also, refactor ptrace.
The implementation was getting long and cluttered the alraedy large
Process.cpp file.
This commit moves the bulk of the implementation to Kernel/Ptrace.cpp,
and factors out peek & poke to separate methods of the Process class.
This commit adds a basic implementation of
the ptrace syscall, which allows one process
(the tracer) to control another process (the tracee).
While a process is being traced, it is stopped whenever a signal is
received (other than SIGCONT).
The tracer can start tracing another thread with PT_ATTACH,
which causes the tracee to stop.
From there, the tracer can use PT_CONTINUE
to continue the execution of the tracee,
or use other request codes (which haven't been implemented yet)
to modify the state of the tracee.
Additional request codes are PT_SYSCALL, which causes the tracee to
continue exection but stop at the next entry or exit from a syscall,
and PT_GETREGS which fethces the last saved register set of the tracee
(can be used to inspect syscall arguments and return value).
A special request code is PT_TRACE_ME, which is issued by the tracee
and causes it to stop when it calls execve and wait for the
tracer to attach.
When stopping a thread with the SIGSTOP signal, we now store the thread
state in Thread::m_stop_state. That state is then restored on SIGCONT.
This fixes an issue where previously-blocked threads would unblock
upon resume. Now they simply resume in the Blocked state, and it's up
to the regular unblocking mechanism to unblock them.
Fixes#1326.
Move timeout management to the ReadBlocker and WriteBlocker classes.
Also get rid of the specialized ReceiveBlocker since it no longer does
anything that ReadBlocker can't do.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
There was a time window between releasing Lock::m_lock and calling into
the lock's WaitQueue where someone else could take m_lock and bring two
threads into a deadlock situation.
Fix this issue by holding Lock::m_lock until interrupts are disabled by
either Thread::wait_on() or WaitQueue::wake_one().
The join_thread() syscall is not supposed to be interruptible by
signals, but it was. And since the process death mechanism piggybacked
on signal interrupts, it was possible to interrupt a pthread_join() by
killing the process that was doing it, leading to confusing due to some
assumptions being made by Thread::finalize() for threads that have a
pending joiner.
This patch fixes the issue by making "interrupted by death" a distinct
block result separate from "interrupted by signal". Then we handle that
state in join_thread() and tidy things up so that thread finalization
doesn't get confused by the pending joiner being gone.
Test: Tests/Kernel/null-deref-crash-during-pthread_join.cpp
This patch introduces a syscall:
int set_thread_boost(int tid, int amount)
You can use this to add a permanent boost value to the effective thread
priority of any thread with your UID (or any thread in the system if
you are the superuser.)
This is quite crude, but opens up some interesting opportunities. :^)
Threads now have numeric priorities with a base priority in the 1-99
range.
Whenever a runnable thread is *not* scheduled, its effective priority
is incremented by 1. This is tracked in Thread::m_extra_priority.
The effective priority of a thread is m_priority + m_extra_priority.
When a runnable thread *is* scheduled, its m_extra_priority is reset to
zero and the effective priority returns to base.
This means that lower-priority threads will always eventually get
scheduled to run, once its effective priority becomes high enough to
exceed the base priority of threads "above" it.
The previous values for ThreadPriority (Low, Normal and High) are now
replaced as follows:
Low -> 10
Normal -> 30
High -> 50
In other words, it will take 20 ticks for a "Low" priority thread to
get to "Normal" effective priority, and another 20 to reach "High".
This is not perfect, and I've used some quite naive data structures,
but I think the mechanism will allow us to build various new and
interesting optimizations, and we can figure out better data structures
later on. :^)
This patch introduces three separate thread queues, one for each thread
priority available to userspace (Low, Normal and High.)
Each queue operates in a round-robin fashion, but we now always prefer
to schedule the highest priority thread that currently wants to run.
There are tons of tweaks and improvements that we can and should make
to this mechanism, but I think this is a step in the right direction.
This makes WindowServer significantly more responsive while one of its
clients is burning CPU. :^)
