libcortex_a9/mutex: added interrupt critical section mask.

master
pca006132 3 years ago committed by Gitea
parent 8f0a6bd5ea
commit 12669124a4
  1. 26
      libcortex_a9/src/asm.rs
  2. 15
      libcortex_a9/src/mutex.rs

@ -40,6 +40,32 @@ pub unsafe fn enable_irq() {
llvm_asm!("cpsie i":::: "volatile");
}
/// Disable IRQ, return if IRQ was originally enabled.
#[inline]
pub unsafe fn enter_critical() -> bool {
let mut cpsr: u32;
llvm_asm!(
"mrs $0, cpsr
cpsid i"
: "=r"(cpsr) ::: "volatile");
(cpsr & (1 << 7)) == 0
}
#[inline]
pub unsafe fn exit_critical(enable: bool) {
// https://stackoverflow.com/questions/40019929/temporarily-disable-interrupts-on-arm
let mask: u32 = if enable {
1 << 7
} else {
0
};
llvm_asm!(
"mrs r1, cpsr
bic r1, r1, $0
msr cpsr_c, r1"
:: "r"(mask) : "r1");
}
/// Exiting IRQ
#[inline]
pub unsafe fn exit_irq() {

@ -41,19 +41,26 @@ impl<T> Mutex<T> {
/// Lock the Mutex, blocks when already locked
pub fn lock(&self) -> MutexGuard<T> {
let mut irq = unsafe { enter_critical() };
while self.locked.compare_and_swap(UNLOCKED, LOCKED, Ordering::Acquire) != UNLOCKED {
wait_for_update();
unsafe {
exit_critical(irq);
wait_for_update();
irq = enter_critical();
}
}
dmb();
MutexGuard { mutex: self }
MutexGuard { mutex: self, irq }
}
pub fn try_lock(&self) -> Option<MutexGuard<T>> {
let irq = unsafe { enter_critical() };
if self.locked.compare_and_swap(UNLOCKED, LOCKED, Ordering::Acquire) != UNLOCKED {
unsafe { exit_critical(irq) };
None
} else {
dmb();
Some(MutexGuard { mutex: self })
Some(MutexGuard { mutex: self, irq })
}
}
@ -69,6 +76,7 @@ impl<T> Mutex<T> {
/// `Deref`/`DerefMutx`
pub struct MutexGuard<'a, T> {
mutex: &'a Mutex<T>,
irq: bool,
}
impl<'a, T> Deref for MutexGuard<'a, T> {
@ -88,5 +96,6 @@ impl<'a, T> DerefMut for MutexGuard<'a, T> {
impl<'a, T> Drop for MutexGuard<'a, T> {
fn drop(&mut self) {
self.mutex.unlock();
unsafe { exit_critical(self.irq) };
}
}

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