Re: kern/56164: System panicked: kernel diagnostic assertion "(target->prt_class == class)" failed: file "/src/src/sys/kern/subr_psref.c", line 296 mismatched psref target class: 0x0 (ref) != 0xffffd2ef411bc940 (expected)

[Andrius V <vezhlys%gmail.com@localhost>]

It seems that the problem may be caused by the race condition when
file->dying is not yet set to true, but sc->sc_dying is already marked
as true (probably by uaudio). Thus, this patch seems to fix my crash
on jabra headset removal  (also mentioned in PR/56172 thread) and
prevents from reaching psref_acquire, which causes assertion panic in
subr_psref.c 296 or 299:

diff --git a/sys/dev/audio/audio.c b/sys/dev/audio/audio.c
index cb5eb00ccce..2e58457e58c 100644
--- a/sys/dev/audio/audio.c
+++ b/sys/dev/audio/audio.c
@@ -1578,7 +1578,7 @@ audio_sc_acquire_fromfile(audio_file_t *file,
struct psref *refp)

        /* If close or audiodetach already ran, tough -- no more audio */
        dying = atomic_load_relaxed(&file->dying);
-       if (dying) {
+       if (dying || file->sc->sc_dying) {
                pserialize_read_exit(s);
                return NULL;

        }

On Tue, May 18, 2021 at 7:05 PM Andrius V <vezhlys%gmail.com@localhost> wrote:
>
> The following reply was made to PR kern/56164; it has been noted by GNATS.
>
> From: Andrius V <vezhlys%gmail.com@localhost>
> To: gnats-bugs%netbsd.org@localhost
> Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost,
>         nia%pkgsrc.org@localhost
> Subject: Re: kern/56164: System panicked: kernel diagnostic assertion
>  "(target->prt_class == class)" failed: file "/src/src/sys/kern/subr_psref.c",
>  line 296 mismatched psref target class: 0x0 (ref) != 0xffffd2ef411bc940 (expected)
> Date: Tue, 18 May 2021 19:02:46 +0300
>
>  Yes, I had similar crash on headset removal, mentioned in
>  port-amd64/56172 thread. I easily reproduce by removing my Jabra
>  headset while sound plays on audiocfg test.
>
>  On Tue, May 18, 2021 at 4:20 PM nia <nia%netbsd.org@localhost> wrote:
>  >
>  > The following reply was made to PR kern/56164; it has been noted by GNATS.
>  >
>  > From: nia <nia%NetBSD.org@localhost>
>  > To: gnats-bugs%netbsd.org@localhost
>  > Cc:
>  > Subject: Re: kern/56164: System panicked: kernel diagnostic assertion
>  >  "(target->prt_class == class)" failed: file
>  >  "/src/src/sys/kern/subr_psref.c", line 296 mismatched psref target class:
>  >  0x0 (ref) != 0xffffd2ef411bc940 (expected)
>  > Date: Tue, 18 May 2021 13:17:12 +0000
>  >
>  >  Gah, it appears to be audio (possibly uaudio) related.
>  >
>  >  [  9180.811329] panic: kernel diagnostic assertion "(target->prt_class == class)" failed: file "/src/src/sys/kern/subr_psref.c", line 296 mismatched psref target class: 0x0 (ref) != 0xfffff76135d8a080 (expected)
>  >  [  9180.811329] cpu2: Begin traceback...
>  >  [  9180.821329] vpanic() at netbsd:vpanic+0x230
>  >  [  9180.821329] db_print_address.cold() at netbsd:db_print_address.cold
>  >  [  9180.821329] psref_acquire() at netbsd:psref_acquire+0x4e0
>  >  [  9180.831327] audio_sc_acquire_fromfile() at netbsd:audio_sc_acquire_fromfile+0xc6
>  >  [  9180.831327] audioclose() at netbsd:audioclose+0x136
>  >  [  9180.841327] closef() at netbsd:closef+0x17f
>  >  [  9180.841327] fd_free() at netbsd:fd_free+0x3c5
>  >  [  9180.841327] exit1() at netbsd:exit1+0x301
>  >  [  9180.851327] sys_exit() at netbsd:sys_exit+0xb0
>  >  [  9180.851327] syscall() at netbsd:syscall+0x26b
>  >  [  9180.861328] --- syscall (number 1) ---
>  >  [  9180.861328] netbsd:syscall+0x26b:
>  >  [  9180.861328] cpu2: End traceback...
>  >
>  >  Still don't have an intact dump, unfortunately...
>  >
>