Changeset f619ec11 in mainline for kernel/arch/ia32/src/drivers/i8254.c

Timestamp:

2007-02-03T21:26:54Z (18 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

cf5ddf6

Parents:

80bcaed

Message:

When clock() is called by an external interrupt dispatched by the IRQ dispatcher,
no spinlock can be held or the kernel will not be preemptive. This fixes Ticket #24.

Formating and indentation fixes.

File:

• kernel/arch/ia32/src/drivers/i8254.c (modified) (2 diffs)

kernel/arch/ia32/src/drivers/i8254.c

@@ -69 +69 @@
 static void i8254_irq_handler(irq_t *irq, void *arg, ...)
 {
+        /*
+         * This IRQ is responsible for kernel preemption.
+         * Nevertheless, we are now holding a spinlock which prevents
+         * preemption. For this particular IRQ, we don't need the
+         * lock. We just release it, call clock() and then reacquire it again.
+         */
+        spinlock_unlock(&irq->lock);
         clock();
+        spinlock_lock(&irq->lock);
 }
 
@@ -137 +145 @@
         o2 |= inb(CLK_PORT1) << 8;
 
-        CPU->delay_loop_const = ((MAGIC_NUMBER*LOOPS)/1000) / ((t1-t2)-(o1-o2)) + (((MAGIC_NUMBER*LOOPS)/1000) % ((t1-t2)-(o1-o2)) ? 1 : 0);
+        CPU->delay_loop_const =
+            ((MAGIC_NUMBER * LOOPS) / 1000) / ((t1 - t2) - (o1 - o2)) +
+            (((MAGIC_NUMBER * LOOPS) / 1000) % ((t1 - t2) - (o1 - o2)) ? 1 : 0);
 
         clk1 = get_cycle();