Re: git: d3690a599586 - stable/15 - devfs: make destroy_dev() a release barrier for cdevpriv destructors runs

From: Konstantin Belousov <kostikbel_at_gmail.com>
Date: Thu, 18 Dec 2025 03:24:26 UTC 
On Wed, Dec 17, 2025 at 09:07:52PM +0000, Vladimir Kondratyev wrote:
> The branch stable/15 has been updated by wulf:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=d3690a5995867e35d4d1dc63127343d4b0a092d6
> 
> commit d3690a5995867e35d4d1dc63127343d4b0a092d6
> Author:     Konstantin Belousov <kib@FreeBSD.org>
> AuthorDate: 2025-10-23 18:37:00 +0000
> Commit:     Vladimir Kondratyev <wulf@FreeBSD.org>
> CommitDate: 2025-12-17 21:05:38 +0000
> 
>     devfs: make destroy_dev() a release barrier for cdevpriv destructors runs
>     
>     Ensure that all destructors for cdevpriv finished running before
>     destroy_dev() returns to the caller.  Otherwise, since
>     devfs_destroy_cdevpriv() removes the cdevpriv data from the list, drops
>     the cdevpriv_mtx, and then starts the destructor, it is possible for
>     destroy_dev() to return before destructor finished in other thread.
>     
>     This should allow drivers to safely remove cdev instance data that might
>     be referenced by cdevpriv data.
>     
>     Diagnosed by:   kevans
>     Reviewed by:    kevans, markj
>     Sponsored by:   The FreeBSD Foundation
>     MFC after:      1 week
>     Differential revision:  https://reviews.freebsd.org/D53303
>     
>     (cherry picked from commit 4dbe6628179d8e6bf400bfdb4bfa869bdc102a56)

I did not merged this to 15 (or 14) because if_tun has a regressions
requiring some fixes from kevans, which were not merged.