* Oleg Nesterov <o...@redhat.com> [2013-01-27 20:48:37]:
> probe_event_enable() does uprobe_register() and only after that sets
> utc->tu and tu->consumer/flags. This can race with uprobe_dispatcher()
> which can miss these assignments or see them out of order. Nothing
> really bad can happen, but this doesn't look clean/safe.
>
> And this does not allow to use uprobe_consumer->filter() we are going
> to add, it is called by uprobe_register() and it needs utc->tu.
>
> Change this code to initialize everything before uprobe_register(), and
> reset tu->consumer/flags if it fails. We can't race with event_disable(),
> the caller holds event_mutex, and if we could the code would be wrong
> anyway.
>
> In fact I think uprobe_trace_consumer should die, it buys nothing but
> complicate the code. We can simply add uprobe_consumer into trace_uprobe.
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
Acked-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> ---
> kernel/trace/trace_uprobe.c | 13 +++++++------
> 1 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 53afabe..94d4ea2 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -552,17 +552,18 @@ static int probe_event_enable(struct trace_uprobe *tu,
> int flag)
> return -EINTR;
>
> utc->cons.handler = uprobe_dispatcher;
> + utc->tu = tu;
> + tu->consumer = utc;
> + tu->flags |= flag;
> +
> ret = uprobe_register(tu->inode, tu->offset, &utc->cons);
> if (ret) {
> + tu->consumer = NULL;
> + tu->flags &= ~flag;
> kfree(utc);
> - return ret;
> }
>
> - tu->flags |= flag;
> - utc->tu = tu;
> - tu->consumer = utc;
> -
> - return 0;
> + return ret;
> }
>
> static void probe_event_disable(struct trace_uprobe *tu, int flag)
> --
> 1.5.5.1
>
--
Thanks and Regards
Srikar Dronamraju
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
