patch-2.4.18 linux/include/asm-cris/irq.h

• Lines: 52
• Date: Tue Jan 8 16:00:08 2002
• Orig file: linux.orig/include/asm-cris/irq.h
• Orig date: Mon Feb 18 20:18:40 2002

diff -Naur -X /home/marcelo/lib/dontdiff linux.orig/include/asm-cris/irq.h linux/include/asm-cris/irq.h
@@ -126,6 +126,9 @@
   /* the asm IRQ handler makes sure the causing IRQ is blocked, then it calls
    * do_IRQ (with irq disabled still). after that it unblocks and jumps to
    * ret_from_intr (entry.S)
+   *
+   * The reason the IRQ is blocked is to allow an sti() before the handler which
+   * will acknowledge the interrupt is run.
    */
 
 #define BUILD_IRQ(nr,mask) \
@@ -151,6 +154,41 @@
           "reti\n\t" \
           "nop\n");
 
+/* This is subtle. The timer interrupt is crucial and it should not be disabled for 
+ * too long. However, if it had been a normal interrupt as per BUILD_IRQ, it would
+ * have been BLOCK'ed, and then softirq's are run before we return here to UNBLOCK.
+ * If the softirq's take too much time to run, the timer irq won't run and the 
+ * watchdog will kill us.
+ *
+ * Furthermore, if a lot of other irq's occur before we return here, the multiple_irq
+ * handler is run and it prioritizes the timer interrupt. However if we had BLOCK'ed
+ * it here, we would not get the multiple_irq at all.
+ *
+ * The non-blocking here is based on the knowledge that the timer interrupt is 
+ * registred as a fast interrupt (SA_INTERRUPT) so that we _know_ there will not
+ * be an sti() before the timer irq handler is run to acknowledge the interrupt.
+ */
+
+#define BUILD_TIMER_IRQ(nr,mask) \
+void IRQ_NAME(nr); \
+void sIRQ_NAME(nr); \
+void BAD_IRQ_NAME(nr); \
+__asm__ ( \
+          ".text\n\t" \
+          "IRQ" #nr "_interrupt:\n\t" \
+	  SAVE_ALL \
+	  "sIRQ" #nr "_interrupt:\n\t" /* shortcut for the multiple irq handler */ \
+	  "moveq "#nr",$r10\n\t" \
+	  "move.d $sp,$r11\n\t" \
+	  "jsr do_IRQ\n\t" /* irq.c, r10 and r11 are arguments */ \
+	  "moveq 0,$r9\n\t" /* make ret_from_intr realise we came from an irq */ \
+	  "jump ret_from_intr\n\t" \
+          "bad_IRQ" #nr "_interrupt:\n\t" \
+	  "push $r0\n\t" \
+	  BLOCK_IRQ(mask,nr) \
+	  "pop $r0\n\t" \
+          "reti\n\t" \
+          "nop\n");
 
 #endif  /* _ASM_IRQ_H */