If you want to record perf events, just enable profiling. This allows us
to add random perf events to programs without littering the file system
with perfcore files.
Making userspace provide a global string ID was silly, and made the API
extremely difficult to use correctly in a global profiling context.
Instead, simply make the kernel do the string ID allocation for us.
This also allows us to convert the string storage to a Vector in the
kernel (and an array in the JSON profile data.)
This syscall allows userspace to register a keyed string that appears in
a new "strings" JSON object in profile output.
This will be used to add custom strings to profile signposts. :^)
We have to disable interrupts before capturing the current Processor*,
or we risk storing the wrong one if we get preempted and resume on a
different CPU.
Caught by the VERIFY in RecursiveSpinLock::unlock()
Currently, to append a UTF-16 view to a StringBuilder, callers must
first convert the view to UTF-8 and then append the copy. Add a UTF-16
overload so callers do not need to hold an entire copy in memory.
This allows tracing the syscalls made by a thread through the kernel's
performance event framework, which is similar in principle to strace.
Currently, this merely logs a stack backtrace to the current thread's
performance event buffer whenever a syscall is made, if profiling is
enabled. Future improvements could include tracing the arguments and
the return value, for example.
Previously, non-blocking read operations on pipes returned EOF instead
of EAGAIN and non-blocking write operations blocked. This fixes
pkgsrc's bmake "eof on job pipe!" error message when running in
non-compatibility mode.
As pointed out by 8infy, this mechanism is racy:
WRITER:
1. ++update1;
2. write_data();
3. ++update2;
READER:
1. do { auto saved = update1;
2. read_data();
3. } while (saved != update2);
The following sequence can lead to a bogus/partial read:
R1 R2 R3
W1 W2 W3
We close this race by incrementing the second update counter first:
WRITER:
1. ++update2;
2. write_data();
3. ++update1;
This fixes the placeholder stub for the SO_ERROR via getsockopt. It
leverages the m_so_error value that each socket maintains. The SO_ERROR
option obtains and then clears this field, which is useful when checking
for errors that occur between socket calls. This uses an integer value
to return the SO_ERROR status.
Resolves#146
This patch adds a vDSO-like mechanism for exposing the current time as
an array of per-clock-source timestamps.
LibC's clock_gettime() calls sys$map_time_page() to map the kernel's
"time page" into the process address space (at a random address, ofc.)
This is only done on first call, and from then on the timestamps are
fetched from the time page.
This first patch only adds support for CLOCK_REALTIME, but eventually
we should be able to support all clock sources this way and get rid of
sys$clock_gettime() in the kernel entirely. :^)
Accesses are synchronized using two atomic integers that are incremented
at the start and finish of the kernel's time page update cycle.
Leave interrupts enabled so that we can still process IRQs. Critical
sections should only prevent preemption by another thread.
Co-authored-by: Tom <tomut@yahoo.com>
By making these functions static we close a window where we could get
preempted after calling Processor::current() and move to another
processor.
Co-authored-by: Tom <tomut@yahoo.com>
This removes Pipes dependency on the UHCIController by introducing a
controller base class. This will be used to implement other controllers
such as OHCI.
Additionally, there can be multiple instances of a UHCI controller.
For example, multiple UHCI instances can be required for systems with
EHCI controllers. EHCI relies on using multiple of either UHCI or OHCI
controllers to drive USB 1.x devices.
This means UHCIController can no longer be a singleton. Multiple
instances of it can now be created and passed to the device and then to
the pipe.
To handle finding and creating these instances, USBManagement has been
introduced. It has the same pattern as the other management classes
such as NetworkManagement.
Port2 logic was errantly using `portsc1` registers, meaning that
the port wouldn't be reset properly. In effect, this puts devices
connected to Port2 in an undefined state.
Processing SMP messages outside of non-SMP mode is a waste of time,
and now that we don't rely on the side effects of calling the message
processing function, let's stop calling it entirely. :^)
We were previously relying on a side effect of the critical section in
smp_process_pending_messages(): when exiting that section, it would
process any pending deferred calls.
Instead of relying on that, make the deferred invocations explicit by
calling deferred_call_execute_pending() in exit_trap().
This ensures that deferred calls get processed before entering the
scheduler at the end of exit_trap(). Since thread unblocking happens
via deferred calls, the threads don't have to wait until the next
scheduling opportunity when they could be ready *now*. :^)
This was the main reason Tom's SMP branch ran slowly in non-SMP mode.
Enter a critical section in Processor::exit_trap so that processing
SMP messages doesn't enable interrupts upon leaving. We need to delay
this until the end where we call into the Scheduler if exiting the
trap results in being outside of a critical section and irq handler.
Co-authored-by: Tom <tomut@yahoo.com>
First off: unregister the region from MemoryManager before unmapping it.
The order of operations here was a bit strange, presumably to avoid a
situation where a fault would happen while unmapping, and the fault
handler would find the MemoryManager region list in an invalid state.
Unregistering it before unmapping sidesteps the whole problem, and
allows us to easily fix another problem: a deadlock could occur due
to inconsistent acquisition order (PageDirectory must come before MM.)
We don't want to be holding the MM lock if it's a user region and we
have to consult the page directory, since that can lead to a deadlock
if we don't already have the page directory lock.
- Use the receiver's per-CPU entry in the message, instead of the
sender's. (Using the sender's entry wasn't safe for broadcast
messages since the same entry ended up on multiple message queues.)
- Retry the CAS until it *succeeds* instead of *fails*. This closes a
race window, and also ensures a correct return value. The return value
is used by the caller to decide whether to broadcast an IPI.
This was the main reason smp=on was so slow. We had CPUs busy-waiting
until someone else triggered an IPI and moved things along.
- Add a CPU pause hint to the spin loop. :^)
It may happen that CPU A manages to page in from the same inode
while we're just entering the same page fault handler on CPU B.
Handle it gracefully by checking if the data has already been paged in
(instead of VERIFY'ing that it hasn't) and then remap the page if that's
the case.
Due to a boolean mistake in smp_return_to_pool(), we didn't retry
pushing the message onto the freelist after a failed attempt.
This caused the message pool to eventually become completely empty
after enough contentious access attempts.
This patch also adds a pause hint to the CPU in the failed attempt
code path.
The kernel panic handler now parses the kernels boot_mode to decide how
to handle the panic. So the previous logic could end up in an panic loop
until we blew out the kernel stack.
Instead only validate the kernel's boot mode once per boot, after
initializing the kernel command line.
