[Patch 1/4] Allow arch-specific cleanup before breakpoint unregistration

Millton Miller
2010-05-25T11:39:53Z

On Tue, 25 May 2010 at 14:43:56 +0530, K.Prasad wrote:
> Certain architectures (such as PowerPC Book III S) have a need to cleanup
> data-structures before the breakpoint is unregistered. This patch introduces
> an arch-specific hook in release_bp_slot() along with a weak definition in
> the form of a stub funciton.
>
> Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
> ---
> kernel/hw_breakpoint.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)

My understanding is weak function definitions must appear in a different C
file than their call sites to work on some toolchains.

Andrew, can you confirm the above statement?

> Index: linux-2.6.ppc64_test/kernel/hw_breakpoint.c
> ===================================================================
> --- linux-2.6.ppc64_test.orig/kernel/hw_breakpoint.c
> +++ linux-2.6.ppc64_test/kernel/hw_breakpoint.c
> @@ -242,6 +242,17 @@ toggle_bp_slot(struct perf_event *bp, bo
> }
>
> /*
> + * Function to perform processor-specific cleanup during unregistration
> + */
> +__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
> +{
> + /*
> + * A weak stub function here for those archs that don't define
> + * it inside arch/.../kernel/hw_breakpoint.c
> + */
> +}
> +
> +/*
> * Contraints to check before allowing this new breakpoint counter:
> *
> * == Non-pinned counter == (Considered as pinned for now)
> @@ -339,6 +350,7 @@ void release_bp_slot(struct perf_event *
> {
> mutex_lock(&nr_bp_mutex);
>
> + arch_unregister_hw_breakpoint(bp);
> __release_bp_slot(bp);
>
> mutex_unlock(&nr_bp_mutex);
>

Since the weak version is empty, should it just be delcared (in
a header, put the comment there) and not defined?

milton