Here is a patch to lockdep.c so it behaves correctly when a kprobe breakpoint is
put on a marker within hardirq tracing functions as long as the marker is within
the lockdep_recursion incremented boundaries. It should apply on 
2.6.20-rc4-git3.

Mathieu

Signed-off-by: Mathieu Desnoyers <[EMAIL PROTECTED]>


@@ -1841,33 +1843,36 @@ void trace_hardirqs_on(void)
        struct task_struct *curr = current;
        unsigned long ip;
 
        if (unlikely(!debug_locks || current->lockdep_recursion))
                return;
 
+       current->lockdep_recursion++;
+       barrier();
+
        if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
-               return;
+               goto end;
 
        if (unlikely(curr->hardirqs_enabled)) {
                debug_atomic_inc(&redundant_hardirqs_on);
-               return;
+               goto end;
        }
        /* we'll do an OFF -> ON transition: */
        curr->hardirqs_enabled = 1;
        ip = (unsigned long) __builtin_return_address(0);
 
        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
-               return;
+               goto end;
        if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
-               return;
+               goto end;
        /*
         * We are going to turn hardirqs on, so set the
         * usage bit for all held locks:
         */
        if (!mark_held_locks(curr, 1, ip))
-               return;
+               goto end;
        /*
         * If we have softirqs enabled, then set the usage
         * bit for all held locks. (disabled hardirqs prevented
@@ -1875,11 +1880,14 @@ void trace_hardirqs_on(void)
         */
        if (curr->softirqs_enabled)
                if (!mark_held_locks(curr, 0, ip))
-                       return;
+                       goto end;
 
        curr->hardirq_enable_ip = ip;
        curr->hardirq_enable_event = ++curr->irq_events;
        debug_atomic_inc(&hardirqs_on_events);
+end:
+       barrier();
+       current->lockdep_recursion--;
 }
 
 EXPORT_SYMBOL(trace_hardirqs_on);
@@ -1888,14 +1896,17 @@ void trace_hardirqs_off(void)
 {
        struct task_struct *curr = current;
 
        if (unlikely(!debug_locks || current->lockdep_recursion))
                return;
 
+       current->lockdep_recursion++;
+       barrier();
+       
        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
-               return;
+               goto end;
 
        if (curr->hardirqs_enabled) {
                /*
@@ -1910,6 +1921,9 @@ void trace_hardirqs_off(void)
                debug_atomic_inc(&hardirqs_off_events);
        } else
                debug_atomic_inc(&redundant_hardirqs_off);
+end:
+       barrier();
+       current->lockdep_recursion--;
 }
 
 EXPORT_SYMBOL(trace_hardirqs_off);

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