Re: [PATCH URCU formal] Remove spurious read-side infinite loops.

Mathieu Desnoyers
2009-02-20T17:15:39Z

* Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote:
> Remove spurious read-side infinite loops from urcu_reader() model.
>

Merged, thanks !

Mathieu

> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> formal-model/urcu.spin | 21 +++++++++++++++++----
> 1 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/formal-model/urcu.spin b/formal-model/urcu.spin
> index 611464b..eea18e8 100644
> --- a/formal-model/urcu.spin
> +++ b/formal-model/urcu.spin
> @@ -27,6 +27,10 @@ bit free = 0; /* Has RCU reclamation happened, e.g., kfree()? */
> bit need_mb = 0; /* =1 says need reader mb, =0 for reader response. */
> byte reader_progress[4];
> /* Count of read-side statement executions. */
> +bit reader_done = 0;
> + /* =0 says reader still running, =1 says done. */
> +bit updater_done = 0;
> + /* =0 says updater still running, =1 says done. */
>
> /* urcu definitions and variables, taken straight from the algorithm. */
>
> @@ -50,7 +54,7 @@ proctype urcu_reader()
> do
> :: need_mb == 1 ->
> need_mb = 0;
> - :: 1 -> skip;
> + :: !updater_done -> skip;
> :: 1 -> break;
> od;
>
> @@ -92,7 +96,7 @@ proctype urcu_reader()
> reader_progress[2] +
> reader_progress[3] == 0) && need_mb == 1 ->
> need_mb = 0;
> - :: 1 -> skip;
> + :: !updater_done -> skip;
> :: 1 -> break;
> od;
> urcu_active_readers = tmp;
> @@ -150,7 +154,7 @@ proctype urcu_reader()
> do
> :: need_mb == 1 ->
> need_mb = 0;
> - :: 1 -> skip;
> + :: !updater_done -> skip;
> :: 1 -> break;
> od;
> :: else -> skip;
> @@ -167,11 +171,14 @@ proctype urcu_reader()
> od;
> assert((tmp_free == 0) || (tmp_removed == 1));
>
> + /* Reader has completed. */
> + reader_done = 1;
> +
> /* Process any late-arriving memory-barrier requests. */
> do
> :: need_mb == 1 ->
> need_mb = 0;
> - :: 1 -> skip;
> + :: !updater_done -> skip;
> :: 1 -> break;
> od;
> }
> @@ -248,6 +255,12 @@ proctype urcu_updater()
>
> /* free-up step, e.g., kfree(). */
> free = 1;
> +
> + /*
> + * Signal updater done, ending any otherwise-infinite loops
> + * in the reading process.
> + */
> + updater_done = 1;
> }
>
> /*
> --
> 1.5.2.5
>

--
Mathieu Desnoyers
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