aboutsummaryrefslogtreecommitdiff
path: root/kernel
diff options
context:
space:
mode:
authorAlex Auvolat <alex.auvolat@ens.fr>2014-12-07 20:26:57 +0100
committerAlex Auvolat <alex.auvolat@ens.fr>2014-12-07 20:26:57 +0100
commit42e92e7e9ab971acd6a1a55e38c0f4e999c1293c (patch)
tree558d2fe64a1c308a021ac1d3f2669f01b357a196 /kernel
parentbd1ed224590700c7568dd6a73a2dadcda238b1d5 (diff)
downloadmacroscope-42e92e7e9ab971acd6a1a55e38c0f4e999c1293c.tar.gz
macroscope-42e92e7e9ab971acd6a1a55e38c0f4e999c1293c.zip
Optimize context switching code on IRQ0.
Diffstat (limited to 'kernel')
-rw-r--r--kernel/l0/context_switch.s32
-rw-r--r--kernel/l0/task.c40
2 files changed, 52 insertions, 20 deletions
diff --git a/kernel/l0/context_switch.s b/kernel/l0/context_switch.s
index 7351997..6738a03 100644
--- a/kernel/l0/context_switch.s
+++ b/kernel/l0/context_switch.s
@@ -11,10 +11,7 @@ save_context_and_enter_scheduler:
mov eax, cr3
push eax
- mov ax, ds ; Lower 16-bits of eax = ds.
- push eax ; save the data segment descriptor
-
- mov eax, [esp+48] ; get address of saved_context structure
+ mov eax, [esp+44] ; get address of saved_context structure
mov [eax], esp ; save esp
mov dword [eax+4], resume_saved_context ; save eip
@@ -23,18 +20,33 @@ save_context_and_enter_scheduler:
resume_saved_context:
pop eax
- mov ds, ax
- mov es, ax
- mov fs, ax
- mov gs, ax
-
- pop eax
mov cr3, eax
popa
popf
ret
+[GLOBAL irq0_save_context_and_enter_scheduler]
+; meant to be called on IRQ0
+; general registers already saved by IRQ handler stub
+; flags already saved by interruption and interruptions disabled
+; only saves CR3
+irq0_save_context_and_enter_scheduler:
+ mov eax, cr3
+ push eax
+
+ mov eax, [esp+8] ; get address of saved_context structure
+ mov [eax], esp ; save esp
+ mov dword [eax+4], resume_saved_irq0_context ; save eip
+
+ mov esp, kernel_stack_top
+ jmp run_scheduler
+
+resume_saved_irq0_context:
+ pop eax
+ mov cr3, eax
+ ret
+
[GLOBAL resume_context]
resume_context:
diff --git a/kernel/l0/task.c b/kernel/l0/task.c
index f8750e6..e31a85c 100644
--- a/kernel/l0/task.c
+++ b/kernel/l0/task.c
@@ -7,6 +7,7 @@
#include <paging.h>
void save_context_and_enter_scheduler(saved_context_t *ctx);
+void irq0_save_context_and_enter_scheduler(saved_context_t *ctx);
void resume_context(saved_context_t *ctx);
task_t *current_task = 0;
@@ -27,6 +28,21 @@ void set_pit_frequency(uint32_t freq) {
outb(0x40, h);
}
+// ============================= //
+// HELPER : IF FLAG MANIPULATION //
+// ============================= //
+
+static inline bool disable_interrupts() {
+ uint32_t eflags;
+ asm volatile("pushf; pop %0" : "=r"(eflags));
+ asm volatile("cli");
+ return (eflags & EFLAGS_IF) != 0;
+}
+
+static inline void resume_interrupts(bool st) {
+ if (st) asm volatile("sti");
+}
+
// ================== //
// THE TASK SCHEDULER //
// ================== //
@@ -63,10 +79,13 @@ task_t* dequeue_task() {
// ================ //
void run_scheduler() {
+ // At this point, interrupts are disabled
// This function is expected NEVER TO RETURN
+
if (current_task != 0 && current_task->state == T_STATE_RUNNING) {
enqueue_task(current_task, true);
}
+
current_task = dequeue_task();
if (current_task != 0) {
resume_context(&current_task->ctx);
@@ -134,9 +153,13 @@ task_t *new_task(entry_t entry) {
return t;
}
+void irq0_handler(registers_t *regs) {
+ if (current_task != 0)
+ irq0_save_context_and_enter_scheduler(&current_task->ctx);
+}
void tasking_setup(entry_t cont, void* arg) {
set_pit_frequency(TASK_SWITCH_FREQUENCY);
- idt_set_irq_handler(IRQ0, yield);
+ idt_set_irq_handler(IRQ0, irq0_handler);
task_t *t = new_task(cont);
ASSERT(t != 0);
@@ -158,9 +181,7 @@ void yield() {
}
void* wait_for_result() {
- uint32_t eflags;
- asm volatile("pushf; pop %0" : "=r"(eflags));
- asm volatile("cli");
+ bool st = disable_interrupts();
if (!current_task->has_result) {
current_task->state = T_STATE_WAITING;
@@ -169,15 +190,14 @@ void* wait_for_result() {
ASSERT(current_task->has_result);
current_task->has_result = false;
- if (eflags & EFLAGS_IF) asm volatile("sti");
+ void *result = current_task->result;
- return current_task->result;
+ resume_interrupts(st);
+ return result;
}
void resume_with_result(task_t *task, void* data, bool run_at_once) {
- uint32_t eflags;
- asm volatile("pushf; pop %0" : "=r"(eflags));
- asm volatile("cli");
+ bool st = disable_interrupts();
task->has_result = true;
task->result = data;
@@ -188,7 +208,7 @@ void resume_with_result(task_t *task, void* data, bool run_at_once) {
}
if (run_at_once) yield();
- if (eflags & EFLAGS_IF) asm volatile("sti");
+ resume_interrupts(st);
}
/* vim: set ts=4 sw=4 tw=0 noet :*/