On Wed, Aug 17, 2011 at 12:36 AM, Alexey Borzenkov <[email protected]> wrote:
> 2. crashes can happen if there's any C-stack switch during garbage
> collection. The reason for this is that Python is creating gc lists on
> the stack, and if during tp_clear there are C-stack switches (as in,
> to kill an alive greenlet/tasklet), then those variables might get
> clobbered. If during the switch there are deallocations, and list head
> is updated, it would lead to random stack corruptions. Now these
> conditions are extremely rare, but they can happen and can lead to
> weird crashes. If anyone is interested you can read how I found this
> issue here:
> https://bitbucket.org/ambroff/greenlet/issue/24/debian-64-errors-with-pydebug
Not a problem in Stackless, see the following code:
#ifdef STACKLESS
/* unlinking may occur in a different tasklet during collection
* so these must not be on the stack
*/
static PyGC_Head unreachable; /* non-problematic unreachable trash */
static PyGC_Head finalizers; /* objects with, & reachable from, __del__ */
#else
PyGC_Head unreachable; /* non-problematic unreachable trash */
PyGC_Head finalizers; /* objects with, & reachable from, __del__ */
#endif
Cheers,
Richard.
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