Subject: Re: bug#58732: installer: finalizers & device destroy segfault

From: Mathieu Othacehe <[email-masked]>
Date: Thu, 10 Nov 2022 13:29:10 +0100

Hey,

> Looking at device.c in Parted, that’s probably the right thing because
> PedDevice objects are kept in a linked list whose head is stored in the
> ‘devices’ global variable of device.c.  So you cannot just free them
> asynchronously from a finalizer thread because they might still be
> accessed from other parts of the library.  This is the explanation that
> should go in the comment, and it’s clearly a good reason not to free
> those PedDevice objects.

If the finalizer was run synchronously when a device is removed from the
weak hash table then things would be OK. The device would be removed
from the global linked list by _device_register. get_device would malloc
a new structure and so on. However finalizers are not run synchronously
so here we are.

> Now, we could provide bindings for ‘ped_device_destroy’ that users could
> explicitly call if they want to (this would be similar to explicit calls
> to ‘close-port’).  We’d arrange to make it idempotent.

Sure.

Thanks for your help on that one. I pushed the proposed patch and updated
Guile-Parted to 0.0.7 in Guix.

Mathieu