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impl Mutex on all shared resources

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document how to write generic code that operates on resources
This commit is contained in:
Jorge Aparicio 2018-11-04 18:50:42 +01:00
parent 16d473a9b6
commit 37a0692a0f
11 changed files with 322 additions and 104 deletions
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20
book/src/by-example/tips.md
View file

@ -1,5 +1,25 @@
# Tips & tricks
## Generics
Resources shared between two or more tasks implement the `Mutex` trait in *all*
contexts, even on those where a critical section is not required to access the
data. This lets you easily write generic code that operates on resources and can
be called from different tasks. Here's one such example:
``` rust
{{#include ../../../examples/generics.rs}}
```
``` console
$ cargo run --example generics
{{#include ../../../ci/expected/generics.run}}```
This also lets you change the static priorities of tasks without having to
rewrite code. If you consistently use `lock`s to access the data behind shared
resources then your code will continue to compile when you change the priority
of tasks.
## Running tasks from RAM
The main goal of moving the specification of RTFM applications to attributes in

6
ci/expected/generics.run Normal file
View file

@ -0,0 +1,6 @@
UART1(STATE = 0)
SHARED: 0 -> 1
UART0(STATE = 0)
SHARED: 1 -> 2
UART1(STATE = 1)
SHARED: 2 -> 4

1
ci/script.sh
View file

@ -57,6 +57,7 @@ main() {
not-send
not-sync
generics
ramfunc
)

2
examples/capacity.rs
View file

@ -23,7 +23,7 @@ macro_rules! println {
#[app(device = lm3s6965)]
const APP: () = {
#[init(spawn = [foo])]
#[init]
fn init() {
rtfm::pend(Interrupt::UART0);
}

74
examples/generics.rs Normal file
View file

@ -0,0 +1,74 @@
//! examples/generics.rs
#![deny(unsafe_code)]
#![deny(warnings)]
#![no_main]
#![no_std]
extern crate panic_semihosting;
use cortex_m_semihosting::debug;
use lm3s6965::Interrupt;
use rtfm::{app, Mutex};
// NOTE: This convenience macro will appear in all the other examples and
// will always look the same
macro_rules! println {
($($tt:tt)*) => {
if let Ok(mut stdout) = cortex_m_semihosting::hio::hstdout() {
use core::fmt::Write;
writeln!(stdout, $($tt)*).ok();
}
};
}
#[app(device = lm3s6965)]
const APP: () = {
static mut SHARED: u32 = 0;
#[init]
fn init() {
rtfm::pend(Interrupt::UART0);
rtfm::pend(Interrupt::UART1);
}
#[interrupt(resources = [SHARED])]
fn UART0() {
static mut STATE: u32 = 0;
println!("UART0(STATE = {})", *STATE);
advance(STATE, resources.SHARED);
rtfm::pend(Interrupt::UART1);
debug::exit(debug::EXIT_SUCCESS);
}
#[interrupt(priority = 2, resources = [SHARED])]
fn UART1() {
static mut STATE: u32 = 0;
println!("UART1(STATE = {})", *STATE);
// just to show that `SHARED` can be accessed directly and ..
*resources.SHARED += 0;
// .. also through a (no-op) `lock`
resources.SHARED.lock(|shared| *shared += 0);
advance(STATE, resources.SHARED);
}
};
fn advance(state: &mut u32, mut shared: impl Mutex<T = u32>) {
*state += 1;
let (old, new) = shared.lock(|shared| {
let old = *shared;
*shared += *state;
(old, *shared)
});
println!("SHARED: {} -> {}", old, new);
}

3
examples/types.rs
View file

@ -8,7 +8,7 @@
extern crate panic_semihosting;
use cortex_m_semihosting::debug;
use rtfm::{app, Instant};
use rtfm::{app, Exclusive, Instant};
#[app(device = lm3s6965)]
const APP: () = {
@ -43,6 +43,7 @@ const APP: () = {
#[task(priority = 2, resources = [SHARED], schedule = [foo], spawn = [foo])]
fn foo() {
let _: Instant = scheduled;
let _: Exclusive<u32> = resources.SHARED;
let _: foo::Resources = resources;
let _: foo::Schedule = schedule;
let _: foo::Spawn = spawn;

34
macros/src/analyze.rs
View file

@ -30,13 +30,14 @@ pub struct Analysis {
pub enum Ownership {
// NOTE priorities and ceilings are "logical" (0 = lowest priority, 255 = highest priority)
Owned { priority: u8 },
CoOwned { priority: u8 },
Shared { ceiling: u8 },
}
impl Ownership {
pub fn needs_lock(&self, priority: u8) -> bool {
match *self {
Ownership::Owned { .. } => false,
Ownership::Owned { .. } | Ownership::CoOwned { .. } => false,
Ownership::Shared { ceiling } => {
debug_assert!(ceiling >= priority);
@ -44,6 +45,13 @@ impl Ownership {
}
}
}
pub fn is_owned(&self) -> bool {
match *self {
Ownership::Owned { .. } => true,
_ => false,
}
}
}
pub struct Dispatcher {
@ -72,18 +80,24 @@ pub fn app(app: &App) -> Analysis {
for (priority, res) in app.resource_accesses() {
if let Some(ownership) = ownerships.get_mut(res) {
match *ownership {
Ownership::Owned { priority: ceiling } | Ownership::Shared { ceiling } => {
if priority != ceiling {
*ownership = Ownership::Shared {
ceiling: cmp::max(ceiling, priority),
};
Ownership::Owned { priority: ceiling }
| Ownership::CoOwned { priority: ceiling }
| Ownership::Shared { ceiling }
if priority != ceiling =>
{
*ownership = Ownership::Shared {
ceiling: cmp::max(ceiling, priority),
};
let res = &app.resources[res];
if res.mutability.is_none() {
assert_sync.insert(res.ty.clone());
}
let res = &app.resources[res];
if res.mutability.is_none() {
assert_sync.insert(res.ty.clone());
}
}
Ownership::Owned { priority: ceiling } if ceiling == priority => {
*ownership = Ownership::CoOwned { priority };
}
_ => {}
}
continue;

68
macros/src/codegen.rs
View file

@ -676,6 +676,7 @@ fn prelude(
}
} else {
let ownership = &analysis.ownerships[name];
let mut exclusive = false;
if ownership.needs_lock(logical_prio) {
may_call_lock = true;
@ -710,28 +711,53 @@ fn prelude(
exprs.push(quote!(#name: <#name as owned_singleton::Singleton>::new()));
} else {
needs_unsafe = true;
defs.push(quote!(pub #name: &'a mut #name));
exprs.push(
quote!(#name: &mut <#name as owned_singleton::Singleton>::new()),
);
if ownership.is_owned() {
defs.push(quote!(pub #name: &'a mut #name));
exprs.push(quote!(
#name: &mut <#name as owned_singleton::Singleton>::new()
));
} else {
may_call_lock = true;
defs.push(quote!(pub #name: rtfm::Exclusive<'a, #name>));
exprs.push(quote!(
#name: rtfm::Exclusive(
&mut <#name as owned_singleton::Singleton>::new()
)
));
}
}
continue;
} else {
defs.push(quote!(pub #name: &#lt #mut_ #ty));
if ownership.is_owned() || mut_.is_none() {
defs.push(quote!(pub #name: &#lt #mut_ #ty));
} else {
exclusive = true;
may_call_lock = true;
defs.push(quote!(pub #name: rtfm::Exclusive<#lt, #ty>));
}
}
}
let alias = &ctxt.statics[name];
needs_unsafe = true;
if initialized {
exprs.push(quote!(#name: &#mut_ #alias));
if exclusive {
exprs.push(quote!(#name: rtfm::Exclusive(&mut #alias)));
} else {
exprs.push(quote!(#name: &#mut_ #alias));
}
} else {
let method = if mut_.is_some() {
quote!(get_mut)
} else {
quote!(get_ref)
};
exprs.push(quote!(#name: #alias.#method() ));
if exclusive {
exprs.push(quote!(#name: rtfm::Exclusive(#alias.#method()) ));
} else {
exprs.push(quote!(#name: #alias.#method() ));
}
}
}
}
@ -1655,19 +1681,23 @@ fn mk_resource(
};
items.push(quote!(
unsafe impl<'a> rtfm::Mutex for #path<'a> {
const CEILING: u8 = #ceiling;
const NVIC_PRIO_BITS: u8 = #device::NVIC_PRIO_BITS;
type Data = #ty;
impl<'a> rtfm::Mutex for #path<'a> {
type T = #ty;
#[inline(always)]
unsafe fn priority(&self) -> &core::cell::Cell<u8> {
&self.#priority
}
#[inline(always)]
fn ptr(&self) -> *mut Self::Data {
unsafe { #ptr }
#[inline]
fn lock<R, F>(&mut self, f: F) -> R
where
F: FnOnce(&mut Self::T) -> R,
{
unsafe {
rtfm::export::claim(
#ptr,
&self.#priority,
#ceiling,
#device::NVIC_PRIO_BITS,
f,
)
}
}
}
));

89
src/export.rs
View file

@ -1,5 +1,8 @@
/// IMPLEMENTATION DETAILS. DO NOT USE ANYTHING IN THIS MODULE
use core::{hint, ptr};
//! IMPLEMENTATION DETAILS. DO NOT USE ANYTHING IN THIS MODULE
#[cfg(not(debug_assertions))]
use core::hint;
use core::{cell::Cell, ptr, u8};
#[cfg(armv7m)]
use cortex_m::register::basepri;
@ -52,7 +55,13 @@ impl<T> MaybeUninit<T> {
if let Some(x) = self.value.as_ref() {
x
} else {
hint::unreachable_unchecked()
match () {
// Try to catch UB when compiling in release with debug assertions enabled
#[cfg(debug_assertions)]
() => unreachable!(),
#[cfg(not(debug_assertions))]
() => hint::unreachable_unchecked(),
}
}
}
@ -60,12 +69,19 @@ impl<T> MaybeUninit<T> {
if let Some(x) = self.value.as_mut() {
x
} else {
hint::unreachable_unchecked()
match () {
// Try to catch UB when compiling in release with debug assertions enabled
#[cfg(debug_assertions)]
() => unreachable!(),
#[cfg(not(debug_assertions))]
() => hint::unreachable_unchecked(),
}
}
}
pub fn set(&mut self, val: T) {
unsafe { ptr::write(&mut self.value, Some(val)) }
// NOTE(volatile) we have observed UB when this uses a plain `ptr::write`
unsafe { ptr::write_volatile(&mut self.value, Some(val)) }
}
}
@ -82,3 +98,66 @@ where
T: Sync,
{
}
#[cfg(armv7m)]
#[inline(always)]
pub unsafe fn claim<T, R, F>(
ptr: *mut T,
priority: &Cell<u8>,
ceiling: u8,
nvic_prio_bits: u8,
f: F,
) -> R
where
F: FnOnce(&mut T) -> R,
{
let current = priority.get();
if priority.get() < ceiling {
if ceiling == (1 << nvic_prio_bits) {
priority.set(u8::MAX);
let r = interrupt::free(|_| f(&mut *ptr));
priority.set(current);
r
} else {
priority.set(ceiling);
basepri::write(logical2hw(ceiling, nvic_prio_bits));
let r = f(&mut *ptr);
basepri::write(logical2hw(current, nvic_prio_bits));
priority.set(current);
r
}
} else {
f(&mut *ptr)
}
}
#[cfg(not(armv7m))]
#[inline(always)]
pub unsafe fn claim<T, R, F>(
ptr: *mut T,
priority: &Cell<u8>,
ceiling: u8,
_nvic_prio_bits: u8,
f: F,
) -> R
where
F: FnOnce(&mut T) -> R,
{
let current = priority.get();
if priority.get() < ceiling {
priority.set(u8::MAX);
let r = interrupt::free(|_| f(&mut *ptr));
priority.set(current);
r
} else {
f(&mut *ptr)
}
}
#[cfg(armv7m)]
#[inline]
fn logical2hw(logical: u8, nvic_prio_bits: u8) -> u8 {
((1 << nvic_prio_bits) - logical) << (8 - nvic_prio_bits)
}

127
src/lib.rs
View file

@ -26,16 +26,14 @@
#![deny(warnings)]
#![no_std]
use core::{cell::Cell, u8};
#[cfg(feature = "timer-queue")]
use core::{cmp::Ordering, ops};
use core::cmp::Ordering;
use core::{fmt, ops};
#[cfg(not(feature = "timer-queue"))]
use cortex_m::peripheral::SYST;
#[cfg(armv7m)]
use cortex_m::register::basepri;
use cortex_m::{
interrupt::{self, Nr},
interrupt::Nr,
peripheral::{CBP, CPUID, DCB, DWT, FPB, FPU, ITM, MPU, NVIC, SCB, TPIU},
};
pub use cortex_m_rtfm_macros::app;
@ -253,81 +251,76 @@ impl U32Ext for u32 {
/// [BASEPRI]) of the current context.
///
/// [BASEPRI]: https://developer.arm.com/products/architecture/cpu-architecture/m-profile/docs/100701/latest/special-purpose-mask-registers
pub unsafe trait Mutex {
/// IMPLEMENTATION DETAIL. DO NOT USE THIS CONSTANT
#[doc(hidden)]
const CEILING: u8;
/// IMPLEMENTATION DETAIL. DO NOT USE THIS CONSTANT
#[doc(hidden)]
const NVIC_PRIO_BITS: u8;
pub trait Mutex {
/// Data protected by the mutex
type Data: Send;
/// IMPLEMENTATION DETAIL. DO NOT USE THIS METHOD
#[doc(hidden)]
unsafe fn priority(&self) -> &Cell<u8>;
/// IMPLEMENTATION DETAIL. DO NOT USE THIS METHOD
#[doc(hidden)]
fn ptr(&self) -> *mut Self::Data;
type T;
/// Creates a critical section and grants temporary access to the protected data
#[inline(always)]
#[cfg(armv7m)]
fn lock<R, F>(&mut self, f: F) -> R
where
F: FnOnce(&mut Self::Data) -> R,
{
unsafe {
let current = self.priority().get();
F: FnOnce(&mut Self::T) -> R;
}
if self.priority().get() < Self::CEILING {
if Self::CEILING == (1 << Self::NVIC_PRIO_BITS) {
self.priority().set(u8::MAX);
let r = interrupt::free(|_| f(&mut *self.ptr()));
self.priority().set(current);
r
} else {
self.priority().set(Self::CEILING);
basepri::write(logical2hw(Self::CEILING, Self::NVIC_PRIO_BITS));
let r = f(&mut *self.ptr());
basepri::write(logical2hw(current, Self::NVIC_PRIO_BITS));
self.priority().set(current);
r
}
} else {
f(&mut *self.ptr())
}
}
}
impl<'a, M> Mutex for &'a mut M
where
M: Mutex,
{
type T = M::T;
/// Creates a critical section and grants temporary access to the protected data
#[cfg(not(armv7m))]
fn lock<R, F>(&mut self, f: F) -> R
where
F: FnOnce(&mut Self::Data) -> R,
F: FnOnce(&mut Self::T) -> R,
{
unsafe {
let current = self.priority().get();
if self.priority().get() < Self::CEILING {
self.priority().set(u8::MAX);
let r = interrupt::free(|_| f(&mut *self.ptr()));
self.priority().set(current);
r
} else {
f(&mut *self.ptr())
}
}
(**self).lock(f)
}
}
#[cfg(armv7m)]
#[inline]
fn logical2hw(logical: u8, nvic_prio_bits: u8) -> u8 {
((1 << nvic_prio_bits) - logical) << (8 - nvic_prio_bits)
/// Newtype over `&'a mut T` that implements the `Mutex` trait
///
/// The `Mutex` implementation for this type is a no-op, no critical section is created
pub struct Exclusive<'a, T>(pub &'a mut T);
impl<'a, T> Mutex for Exclusive<'a, T> {
type T = T;
fn lock<R, F>(&mut self, f: F) -> R
where
F: FnOnce(&mut Self::T) -> R,
{
f(self.0)
}
}
impl<'a, T> fmt::Debug for Exclusive<'a, T>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
(**self).fmt(f)
}
}
impl<'a, T> fmt::Display for Exclusive<'a, T>
where
T: fmt::Display,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
(**self).fmt(f)
}
}
impl<'a, T> ops::Deref for Exclusive<'a, T> {
type Target = T;
fn deref(&self) -> &T {
self.0
}
}
impl<'a, T> ops::DerefMut for Exclusive<'a, T> {
fn deref_mut(&mut self) -> &mut T {
self.0
}
}
/// Sets the given `interrupt` as pending

2
src/tq.rs
View file

@ -91,7 +91,7 @@ where
#[inline(always)]
pub fn isr<TQ, T, N, F>(mut tq: TQ, mut f: F)
where
TQ: Mutex<Data = TimerQueue<T, N>>,
TQ: Mutex<T = TimerQueue<T, N>>,
T: Copy + Send,
N: ArrayLength<NotReady<T>>,
F: FnMut(T, u8),