[Stackless] assert in schedule_task_destruct
richard.m.tew at gmail.com
Thu May 7 20:07:06 CEST 2009
On Thu, May 7, 2009 at 1:21 PM, Richard Tew <richard.m.tew at gmail.com> wrote:
> On Thu, May 7, 2009 at 1:17 PM, Manley, Tom <Tom.Manley at spectrumdsi.com> wrote:
>> To hit the assert I start the interpreter from VS2K8, import stackless, and then paste the commands into the interpreter. I just tried recreating your steps by putting the commands in a script and running it directly, and that worked fine, i.e. does not assert. I also tried starting the interpreter from VS2K8 and importing the script and it worked there as well.
> Given this, the assertion is harmless. I still need to reconcile
> fixes made in different branches, and the fix for this has been made
> in py3k branch, and still needs to be merged over. Feel free to
> ignore it.
On Thu, May 7, 2009 at 2:04 PM, richard.tew <python-checkins at python.org> wrote:
> Author: richard.tew
> Date: Thu May 7 20:04:08 2009
> New Revision: 72433
> Merged r64818 from py3k.
> When a main tasklet is destroyed, it was expected that there wouldn't be a current tasklet if the recursion count was higher than 0. This is not correct in the case the tasklet was created by an interpreter command, as each creates a new main tasklet, and the creation of a new tasklet within that will leave it in the scheduler as the current tasklet, as the main exits.
> Why did this not error in older versions of Python? I do not know. But the fix makes sense, and the recursion count being greater than 0 is valid (it was that way before we created the main tasklet).
> Modified: stackless/branches/release26-maint/Stackless/module/scheduling.c
> --- stackless/branches/release26-maint/Stackless/module/scheduling.c (original)
> +++ stackless/branches/release26-maint/Stackless/module/scheduling.c Thu May 7 20:04:08 2009
> @@ -1026,12 +1026,19 @@
> /* update what's not yet updated
> Normal tasklets when created have no recursion depth yet, but the main
> tasklet is initialized in the middle of an existing indeterminate call
> stack. Therefore it is not guaranteed that there is not a pre-existing
> recursion depth from before its initialization.
> + Previously, we exited a main tasklet with the expectation that there would
> + be no current one. This is incorrect, and the case of the interpreter where
> + each command creates a new main tasklet to create a new tasklet, which is
> + scheduled (made the current now) but not run yet, means we need to expand
> + this check.
> - assert(ts->recursion_depth == 0 || ts->st.main == NULL && ts->st.current == NULL && prev == next);
> + assert(ts->recursion_depth == 0 || ts->st.main == NULL && ts->st.current != next && prev == next);
> prev->recursion_depth = 0;
> assert(ts->frame == NULL);
> prev->f.frame = NULL;
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