Move PIT_TICKS to context::switch.

src/arch/aarch64/interrupt/irq.rs

@@ -9,9 +9,6 @@ use crate::time;
 
 use crate::{exception_stack};
 
-//resets to 0 in context::switch()
-pub static PIT_TICKS: AtomicUsize = ATOMIC_USIZE_INIT;
-
 exception_stack!(irq_at_el0, |stack| {
     match gic::irq_ack() {
         30 => irq_handler_gentimer(30),
@@ -56,10 +53,8 @@ pub unsafe fn irq_handler_gentimer(irq: u32) {
 
     timeout::trigger();
 
-    // Switch after 3 ticks (about 6.75 ms)
-    if PIT_TICKS.fetch_add(1, Ordering::SeqCst) >= 2 {
-        let _ = context::switch();
-    }
+    context::switch::tick();
+
     trigger(irq);
     GENTIMER.reload_count();
 }

src/arch/x86/interrupt/ipi.rs

@@ -1,9 +1,7 @@
-use core::sync::atomic::Ordering;
 use x86::tlb;
 
 use crate::context;
 use crate::device::local_apic::LOCAL_APIC;
-use super::irq::PIT_TICKS;
 
 interrupt!(wakeup, || {
     LOCAL_APIC.eoi();
@@ -24,8 +22,6 @@ interrupt!(switch, || {
 interrupt!(pit, || {
     LOCAL_APIC.eoi();
 
-    // Switch after 3 ticks (about 6.75 ms)
-    if PIT_TICKS.fetch_add(1, Ordering::SeqCst) >= 2 {
-        let _ = context::switch();
-    }
+    // Switch after a sufficent amount of time since the last switch.
+    context::switch::tick();
 });

src/arch/x86/interrupt/irq.rs

@@ -11,10 +11,6 @@ use crate::scheme::debug::{debug_input, debug_notify};
 use crate::scheme::serio::serio_input;
 use crate::{context, time};
 
-//resets to 0 in context::switch()
-#[thread_local]
-pub static PIT_TICKS: AtomicUsize = AtomicUsize::new(0);
-
 #[repr(u8)]
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum IrqMethod {
@@ -149,10 +145,8 @@ interrupt_stack!(pit_stack, |_stack| {
     // Any better way of doing this?
     timeout::trigger();
 
-    // Switch after 3 ticks (about 6.75 ms)
-    if PIT_TICKS.fetch_add(1, Ordering::SeqCst) >= 2 {
-        let _ = context::switch();
-    }
+    // Switch after a sufficent amount of time since the last switch.
+    context::switch::tick();
 });
 
 interrupt!(keyboard, || {

src/arch/x86_64/interrupt/ipi.rs

@@ -1,9 +1,7 @@
-use core::sync::atomic::Ordering;
 use x86::tlb;
 
 use crate::context;
 use crate::device::local_apic::LOCAL_APIC;
-use super::irq::PIT_TICKS;
 
 interrupt!(wakeup, || {
     LOCAL_APIC.eoi();
@@ -24,8 +22,6 @@ interrupt!(switch, || {
 interrupt!(pit, || {
     LOCAL_APIC.eoi();
 
-    // Switch after 3 ticks (about 6.75 ms)
-    if PIT_TICKS.fetch_add(1, Ordering::SeqCst) >= 2 {
-        let _ = context::switch();
-    }
+    // Switch after a sufficient amount of time since the last switch.
+    context::switch::tick();
 });

src/arch/x86_64/interrupt/irq.rs

@@ -11,10 +11,6 @@ use crate::scheme::debug::{debug_input, debug_notify};
 use crate::scheme::serio::serio_input;
 use crate::{context, time};
 
-//resets to 0 in context::switch()
-#[thread_local]
-pub static PIT_TICKS: AtomicUsize = AtomicUsize::new(0);
-
 #[repr(u8)]
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum IrqMethod {
@@ -149,10 +145,8 @@ interrupt_stack!(pit_stack, |_stack| {
     // Any better way of doing this?
     timeout::trigger();
 
-    // Switch after 3 ticks (about 6.75 ms)
-    if PIT_TICKS.fetch_add(1, Ordering::SeqCst) >= 2 {
-        let _ = context::switch();
-    }
+    // Switch after a sufficient amount of time since the last switch.
+    context::switch::tick();
 });
 
 interrupt!(keyboard, || {

src/context/mod.rs

@@ -34,7 +34,7 @@ pub mod context;
 mod list;
 
 /// Context switch function
-mod switch;
+pub mod switch;
 
 /// File struct - defines a scheme and a file number
 pub mod file;

src/context/switch.rs

@@ -10,7 +10,6 @@ use crate::context::signal::signal_handler;
 use crate::context::{arch, contexts, Context, CONTEXT_ID};
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 use crate::gdt;
-use crate::interrupt::irq::PIT_TICKS;
 use crate::interrupt;
 use crate::ptrace;
 use crate::time;
@@ -91,6 +90,20 @@ struct SwitchResult {
 #[thread_local]
 static SWITCH_RESULT: Cell<Option<SwitchResult>> = Cell::new(None);
 
+//resets to 0 in context::switch()
+#[thread_local]
+pub static PIT_TICKS: Cell<usize> = Cell::new(0);
+
+pub fn tick() {
+    let new_ticks = PIT_TICKS.get() + 1;
+    PIT_TICKS.set(new_ticks);
+
+    // Switch after 3 ticks (about 6.75 ms)
+    if new_ticks >= 3 {
+        let _ = unsafe { switch() };
+    }
+}
+
 pub unsafe extern "C" fn switch_finish_hook() {
     if let Some(SwitchResult { prev_lock, next_lock }) = SWITCH_RESULT.take() {
         prev_lock.force_write_unlock();
@@ -110,7 +123,7 @@ pub unsafe extern "C" fn switch_finish_hook() {
 pub unsafe fn switch() -> bool {
     // TODO: Better memory orderings?
     //set PIT Interrupt counter to 0, giving each process same amount of PIT ticks
-    let _ticks = PIT_TICKS.swap(0, Ordering::SeqCst);
+    PIT_TICKS.set(0);
 
     // Set the global lock to avoid the unsafe operations below from causing issues
     while arch::CONTEXT_SWITCH_LOCK.compare_exchange_weak(false, true, Ordering::SeqCst, Ordering::Relaxed).is_err() {