Re: [PATCH 2/2] lockdep reentrancy

Andrew Morton
2007-01-24T04:30:27Z

On Tue, 16 Jan 2007 12:56:31 -0500
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> 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 <mathieu.desnoyers@polymtl.ca>
>
>
> @@ -1841,33 +1843,36 @@ void trace_hardirqs_on(void)

You lost the patch headers.

> struct task_struct *curr = current;
> unsigned long ip;
>
> if (unlikely(!debug_locks || current->lockdep_recursion))
> return;
>
> + current->lockdep_recursion++;
> + barrier();

Why can't we use lockdep_off() here?

> 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--;

lockdep_on()?

> }
>
> 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();

lockdep_off()?

> 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--;

lockdep_on()?