[Simulavr-devel] [PATCH] FIX: Remove delayed ISR calls when clearing the interrupt's flag.

[Stan Behrens]

If interrupts are globally disabled and a condition occurs where an ISR
would be executed, they will be delayed until interrupts are enabled
again (SEI or RETI).
On a real MCU the interrupt's condition is saved in hardware through the
wiring of the MCU. In the simulator we have a sorted list for delayed
interrupts (irqPartnerList) which has to be kept in sync with the
simulated hardware state.
This patch fixes a situation where the already scheduled execution
of an ISR is not removed from the list while the hardware state changed
through clearing the interrupt's flag.
---
 src/hwtimer/timerirq.cpp |   14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/hwtimer/timerirq.cpp b/src/hwtimer/timerirq.cpp
index 279d4a7..a05e8d7 100644
--- a/src/hwtimer/timerirq.cpp
+++ b/src/hwtimer/timerirq.cpp
@@ -129,9 +129,19 @@ unsigned char TimerIRQRegister::set_from_reg(const 
IOSpecialReg* reg, unsigned c
                 irqsystem->SetIrqFlag(this, lines[idx]->irqvector);
         }
         irqmask = nv;
-    } else
+    } else {
+        // Get all interrupt flags that are actually cleared with this 
instruction.
+        unsigned char reset = nv & bitmask & irqflags;
+
         // reset flag, if written with 1
-        irqflags ^= nv & bitmask & irqflags;
+        irqflags ^= reset;
+
+        // Walk through resetting flags beginning with the LSB ...
+        for(unsigned char idx = 0; idx < lines.size(); ++idx)
+            if(reset & (1<<idx))
+                // ... and remove there pending calls from the irq system.
+                ClearIrqFlag(lines[idx]->irqvector);
+    }
     return nv;
 }
 
-- 
1.7.5.4