libcortex_a9/mutex: added interrupt critical section mask.
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8f0a6bd5ea
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12669124a4
@ -40,6 +40,32 @@ pub unsafe fn enable_irq() {
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llvm_asm!("cpsie i":::: "volatile");
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llvm_asm!("cpsie i":::: "volatile");
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}
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}
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/// Disable IRQ, return if IRQ was originally enabled.
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#[inline]
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pub unsafe fn enter_critical() -> bool {
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let mut cpsr: u32;
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llvm_asm!(
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"mrs $0, cpsr
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cpsid i"
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: "=r"(cpsr) ::: "volatile");
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(cpsr & (1 << 7)) == 0
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}
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#[inline]
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pub unsafe fn exit_critical(enable: bool) {
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// https://stackoverflow.com/questions/40019929/temporarily-disable-interrupts-on-arm
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let mask: u32 = if enable {
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1 << 7
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} else {
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0
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};
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llvm_asm!(
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"mrs r1, cpsr
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bic r1, r1, $0
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msr cpsr_c, r1"
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:: "r"(mask) : "r1");
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}
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/// Exiting IRQ
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/// Exiting IRQ
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#[inline]
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#[inline]
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pub unsafe fn exit_irq() {
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pub unsafe fn exit_irq() {
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@ -41,19 +41,26 @@ impl<T> Mutex<T> {
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/// Lock the Mutex, blocks when already locked
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/// Lock the Mutex, blocks when already locked
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pub fn lock(&self) -> MutexGuard<T> {
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pub fn lock(&self) -> MutexGuard<T> {
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let mut irq = unsafe { enter_critical() };
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while self.locked.compare_and_swap(UNLOCKED, LOCKED, Ordering::Acquire) != UNLOCKED {
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while self.locked.compare_and_swap(UNLOCKED, LOCKED, Ordering::Acquire) != UNLOCKED {
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unsafe {
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exit_critical(irq);
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wait_for_update();
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wait_for_update();
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irq = enter_critical();
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}
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}
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}
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dmb();
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dmb();
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MutexGuard { mutex: self }
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MutexGuard { mutex: self, irq }
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}
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}
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pub fn try_lock(&self) -> Option<MutexGuard<T>> {
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pub fn try_lock(&self) -> Option<MutexGuard<T>> {
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let irq = unsafe { enter_critical() };
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if self.locked.compare_and_swap(UNLOCKED, LOCKED, Ordering::Acquire) != UNLOCKED {
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if self.locked.compare_and_swap(UNLOCKED, LOCKED, Ordering::Acquire) != UNLOCKED {
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unsafe { exit_critical(irq) };
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None
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None
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} else {
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} else {
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dmb();
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dmb();
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Some(MutexGuard { mutex: self })
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Some(MutexGuard { mutex: self, irq })
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}
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}
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}
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}
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@ -69,6 +76,7 @@ impl<T> Mutex<T> {
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/// `Deref`/`DerefMutx`
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/// `Deref`/`DerefMutx`
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pub struct MutexGuard<'a, T> {
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pub struct MutexGuard<'a, T> {
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mutex: &'a Mutex<T>,
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mutex: &'a Mutex<T>,
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irq: bool,
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}
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}
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impl<'a, T> Deref for MutexGuard<'a, T> {
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impl<'a, T> Deref for MutexGuard<'a, T> {
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@ -88,5 +96,6 @@ impl<'a, T> DerefMut for MutexGuard<'a, T> {
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impl<'a, T> Drop for MutexGuard<'a, T> {
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impl<'a, T> Drop for MutexGuard<'a, T> {
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fn drop(&mut self) {
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fn drop(&mut self) {
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self.mutex.unlock();
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self.mutex.unlock();
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unsafe { exit_critical(self.irq) };
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}
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}
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}
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}
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