The previous patch didn't properly restore thread IDs when switching
contexts -- there were spots where we missed things, and spots where we
were double-borrowing.
Fix these corner cases.
Signed-off-by: Sean Cross <sean@xobs.io>
Note the current thread in the original process when its quantum
expires. This will allow us to clean up after ourselves when a context
switch occurs, and will help to prevent thread starvation.
Signed-off-by: Sean Cross <sean@xobs.io>
Currently, returning a Message (e.g. a Scalar1, Scalar2, or
MemoryMessage) always results in a context switch from the server to the
client. This is what makes these syscalls cheaper.
However, this results in process starvation. For example, if three
processes send a message to a server, then the server will only be able
to respond to one of those messages at a time. This works well with a
lightly-loaded system, but quickly falls apart when many threads are
running.
Keep track of which process and thread were originally switched to as
part of the `SwitchTo` call. If the Server is responding to a message
and owns the current quantum, don't immediately switch to the Client
thread.
Signed-off-by: Sean Cross <sean@xobs.io>
Unify scalar return calls so that we only have one return path rather
than three.
We can almost unify memory returning as well, but it's not quite there.
Signed-off-by: Sean Cross <sean@xobs.io>
Add notes on how to properly hand memory to userspace. This does not yet
work, but is committed here as a work-in-progress.
Signed-off-by: Sean Cross <sean@xobs.io>
When waiting on a thread, it may be the case that the thread we're
joining has exited already. In this case, the correct approach is to
resume execution rather than switching to the parent process.
This fixes an issue where `SWITCHTO_CALLER` is None when joining a
short-lived thread.
Signed-off-by: Sean Cross <sean@xobs.io>
When attempting to return an invalid item, return `DoubleFree`. This is
because such cases are most likely due to instances where a message was
responded to twice.
Signed-off-by: Sean Cross <sean@xobs.io>
Fix a segfault that occurred when using ReplyAndReceiveNext on hosted
mode. This now properly passes memory messages back to the client.
Signed-off-by: Sean Cross <sean@xobs.io>
Implement `ReplyAndReceiveNext` as a syscall. This will reply to a
message, pull the next message out of the queue, and then re-queue the
server to run. This should make servers much more responsive.
This patch has been tested on both hosted and native modes.
Signed-off-by: Sean Cross <sean@xobs.io>
this will help speed up performance profiling as we can
resolve the physical address of the performance buffer allocated
in RAM and use a USB command to read it out, instead of streaming
it over serial.
Implement the syscall to adjust a process' limit. Currently this
only supports adjusting the heap maximum and the heap size.
In order to adjust a limit, you must first present the current limit.
This can be obtained by requesting a bogus value. The current limit is
returned as part of the result.
Signed-off-by: Sean Cross <sean@xobs.io>
Return the heap size and offset when decreasing the heap. Additionally,
return the heap size when increasing the heap by 0 bytes.
Signed-off-by: Sean Cross <sean@xobs.io>
Implement a functioning CreateProcess syscall on riscv. This call
creates a server in the child process, and connects the server to the
parent. The parent can communicate with the child process using this
server.
The Server ID is passed as four `u32` values to the entrypoint function.
This can be reassembled into something that can then be passed to the
`ReceiveMessage` syscall.
Signed-off-by: Sean Cross <sean@xobs.io>
We now us `ProcessStartup` as the return type. This builds in tset
mode, hosted mode, and RISC-V mode.
Process Startup is still not implemented for RISC-V mode.
Signed-off-by: Sean Cross <sean@xobs.io>
Turns out we didn't end up needing this capability, so, commenting it
out because it is a shy too powerful and is like packing a live
mortar shell in a storage unit: eventually, someone is going to
get hurt, even though it seems mostly harmless at the moment.
Code just commented out in case we need this feature in the future,
but, the main reason it was asked for (the PDDB) was accomplished
without it.
Mark the private fields in a `MemoryRange` struct as being private. This
allows us to perform operations on the memory range armed with the
knowledge that the entire range is valid and unaliased.
Signed-off-by: Sean Cross <sean@xobs.io>
This function allows for creating arbitrary memory ranges. Mark this
function as `unsafe` in order to warn users that this can be used to
create invalid memory regions.
Signed-off-by: Sean Cross <sean@xobs.io>
Switch to the message client when returning memory in Hosted mode. This
properly marks a process as ready-to-run, which was otherwise not
correctly done.
Signed-off-by: Sean Cross <sean@xobs.io>
This enables processes to be "suspended" by going into a Debug state.
Messages will back up and processes will continue to be scheduled around
the suspended process, while the system will continue to operate.
Signed-off-by: Sean Cross <sean@xobs.io>
Due to several errors, multi-page lending did not work properly.
To begin with, if a page was not allocated then it would not be able to
be sent. That is, if you allocated 8192 bytes but only ever accessed the
first 4096 bytes, then an error would be encountered when lending the
unaccessed upper page.
Furthermore, due to a striding error in accessing pointers, half-pages
were treated as full pages.
Signed-off-by: Sean Cross <sean@xobs.io>
