From nobody Mon Mar 07 20:54:26 2022 X-Original-To: freebsd-arm@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id CD11219F3841; Mon, 7 Mar 2022 20:54:29 +0000 (UTC) (envelope-from SRS0=34E+=TS=klop.ws=ronald-lists@realworks.nl) Received: from smtp-relay-int.realworks.nl (smtp-relay-int.realworks.nl [194.109.157.24]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4KC9gT00PNz3rwN; Mon, 7 Mar 2022 20:54:28 +0000 (UTC) (envelope-from SRS0=34E+=TS=klop.ws=ronald-lists@realworks.nl) Date: Mon, 7 Mar 2022 21:54:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=klop.ws; s=rw2; t=1646686466; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5WNf6aELst4UDlOXYajv/u8+6WSw4kSQiOjBQwM7D+M=; b=jAlcHq6vTJ7WTgxh0OfUPPh78lWhxKuZAUdEMpYO5yY2sZ6V5+/e4cgpvogNum7vStsSAj RumkfT+eKvfn/gyo3UserZHdTngoyzsNoVlH+jL5IGLuM36gkkCgXmWjgN9zgfoo8wYX1L YGqk2OtcZX6e3d+mBc1Vxo+p9RC4dHBmuXDTiPQmI6OM0H0sxbBkxrhZ5KMUNwr/R28BVf R9MljJf/KNllvctYD0HCQOPz8qckUKIFCCu5mWuKjL3dUyozp9GFcWS5D+QOyi+AB3Qkk/ 8OVkU0uvkCaM7gL7nLu4NAmoEu0BECadRgWqNK02Bw8aYQvWhje3o6CY928Tzw== From: Ronald Klop To: Mark Johnston Cc: bob prohaska , Mark Millard , freebsd-arm@freebsd.org, freebsd-current Message-ID: <1302689164.173.1646686466515@mailrelay> In-Reply-To: References: <1800459695.1.1646649539521@mailrelay> <132978150.92.1646660769467@mailrelay> Subject: Re: panic: data abort in critical section or under mutex (was: Re: panic: Unknown kernel exception 0 esr_el1 2000000 (on 14-CURRENT/aarch64 Feb 28)) List-Id: Porting FreeBSD to ARM processors List-Archive: https://lists.freebsd.org/archives/freebsd-arm List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-arm@freebsd.org MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_172_1254189170.1646686466401" X-Mailer: Realworks (599.211.aa1e011) Importance: Normal X-Priority: 3 (Normal) X-Rspamd-Queue-Id: 4KC9gT00PNz3rwN X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=klop.ws header.s=rw2 header.b=jAlcHq6v; dmarc=pass (policy=quarantine) header.from=klop.ws; spf=pass (mx1.freebsd.org: domain of "SRS0=34E@realworks.nl" designates 194.109.157.24 as permitted sender) smtp.mailfrom="SRS0=34E@realworks.nl" X-Spamd-Result: default: False [-3.20 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[klop.ws:s=rw2]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+ip4:194.109.157.0/24]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[multipart/alternative,text/plain]; RCPT_COUNT_FIVE(0.00)[5]; TO_MATCH_ENVRCPT_SOME(0.00)[]; DKIM_TRACE(0.00)[klop.ws:+]; DMARC_POLICY_ALLOW(-0.50)[klop.ws,quarantine]; HAS_X_PRIO_THREE(0.00)[3]; NEURAL_HAM_SHORT(-1.00)[-1.000]; MLMMJ_DEST(0.00)[freebsd-arm,freebsd-current]; FORGED_SENDER(0.30)[ronald-lists@klop.ws,SRS0=34E@realworks.nl]; RCVD_COUNT_ZERO(0.00)[0]; MIME_TRACE(0.00)[0:+,1:+,2:~]; MID_RHS_NOT_FQDN(0.50)[]; ASN(0.00)[asn:3265, ipnet:194.109.0.0/16, country:NL]; TAGGED_FROM(0.00)[=TS=klop.ws=ronald-lists]; FROM_NEQ_ENVFROM(0.00)[ronald-lists@klop.ws,SRS0=34E@realworks.nl]; FREEMAIL_CC(0.00)[www.zefox.net,yahoo.com,freebsd.org] X-ThisMailContainsUnwantedMimeParts: N ------=_Part_172_1254189170.1646686466401 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Van: Mark Johnston Datum: maandag, 7 maart 2022 16:13 Aan: Ronald Klop CC: bob prohaska , Mark Millard , freebsd-arm@freebsd.org, freebsd-current Onderwerp: Re: panic: data abort in critical section or under mutex (was: Re: panic: Unknown kernel exception 0 esr_el1 2000000 (on 14-CURRENT/aarch64 Feb 28)) > > On Mon, Mar 07, 2022 at 02:46:09PM +0100, Ronald Klop wrote: > > Dear Mark Johnston, > > > > I did some binary search in the kernels and came to the conclusion that https://cgit.freebsd.org/src/commit/?id=1517b8d5a7f58897200497811de1b18809c07d3e still works and https://cgit.freebsd.org/src/commit/?id=407c34e735b5d17e2be574808a09e6d729b0a45a panics. > > > > I suspect your commit in https://cgit.freebsd.org/src/commit/?id=c84bb8cd771ce4bed58152e47a32dda470bef23a. > > > > Last panic: > > > > panic: vm_fault failed: ffff00000046e708 error 1 > > cpuid = 1 > > time = 1646660058 > > KDB: stack backtrace: > > db_trace_self() at db_trace_self > > db_trace_self_wrapper() at db_trace_self_wrapper+0x30 > > vpanic() at vpanic+0x174 > > panic() at panic+0x44 > > data_abort() at data_abort+0x2e8 > > handle_el1h_sync() at handle_el1h_sync+0x10 > > --- exception, esr 0x96000004 > > _rm_rlock_debug() at _rm_rlock_debug+0x8c > > osd_get() at osd_get+0x5c > > zio_execute() at zio_execute+0xf8 > > taskqueue_run_locked() at taskqueue_run_locked+0x178 > > taskqueue_thread_loop() at taskqueue_thread_loop+0xc8 > > fork_exit() at fork_exit+0x74 > > fork_trampoline() at fork_trampoline+0x14 > > KDB: enter: panic > > [ thread pid 0 tid 100129 ] > > Stopped at kdb_enter+0x44: undefined f902011f > > db> > > > > A more recent kernel (912df91) still panics. See below. > > > > Do you have time to look into this? What can I provide in information to help? > > Hmm. So after my rmlock commits, we have the following disassembly for > _rm_rlock() (with a few annotations added by me). Note that the pcpu > pointer is stored in register x18 by convention. > > 0xffff00000046e304 <+0>: stp x29, x30, [sp, #-16]! > 0xffff00000046e308 <+4>: mov x29, sp > 0xffff00000046e30c <+8>: ldr x8, [x18] > 0xffff00000046e310 <+12>: ldr x9, [x18] > 0xffff00000046e314 <+16>: ldr x10, [x18] > 0xffff00000046e318 <+20>: cmp x9, x10 > 0xffff00000046e31c <+24>: b.ne 0xffff00000046e3cc <_rm_rlock+200> // b.any > 0xffff00000046e320 <+28>: ldr x9, [x18] > 0xffff00000046e324 <+32>: ldrh w9, [x9, #314] > 0xffff00000046e328 <+36>: cbnz w9, 0xffff00000046e3c0 <_rm_rlock+188> > 0xffff00000046e32c <+40>: str wzr, [x1, #32] > 0xffff00000046e330 <+44>: stp x0, x8, [x1, #16] > 0xffff00000046e334 <+48>: ldrb w9, [x0, #10] > 0xffff00000046e338 <+52>: tbz w9, #4, 0xffff00000046e358 <_rm_rlock+84> > 0xffff00000046e33c <+56>: ldr x9, [x18] > 0xffff00000046e340 <+60>: ldr w10, [x9, #888] > 0xffff00000046e344 <+64>: add w10, w10, #0x1 > 0xffff00000046e348 <+68>: str w10, [x9, #888] > 0xffff00000046e34c <+72>: ldr x9, [x18] > 0xffff00000046e350 <+76>: ldr w9, [x9, #888] > 0xffff00000046e354 <+80>: cbz w9, 0xffff00000046e3f4 <_rm_rlock+240> > 0xffff00000046e358 <+84>: ldr w9, [x8, #1212] > 0xffff00000046e35c <+88>: add x10, x18, #0x90 > 0xffff00000046e360 <+92>: add w9, w9, #0x1 > 0xffff00000046e364 <+96>: str w9, [x8, #1212] <------- critical_enter > 0xffff00000046e368 <+100>: str x10, [x1, #8] > 0xffff00000046e36c <+104>: ldr x9, [x18, #144] > 0xffff00000046e370 <+108>: str x9, [x1] > 0xffff00000046e374 <+112>: str x1, [x9, #8] > 0xffff00000046e378 <+116>: str x1, [x18, #144] > 0xffff00000046e37c <+120>: ldr x9, [x18] > 0xffff00000046e380 <+124>: ldr w10, [x9, #356] > 0xffff00000046e384 <+128>: add w10, w10, #0x1 > 0xffff00000046e388 <+132>: str w10, [x9, #356] > 0xffff00000046e38c <+136>: ldr w9, [x8, #1212] > 0xffff00000046e390 <+140>: sub w9, w9, #0x1 > 0xffff00000046e394 <+144>: str w9, [x8, #1212] <------- critical_exit > 0xffff00000046e398 <+148>: ldrb w8, [x8, #304] > 0xffff00000046e39c <+152>: ldr w9, [x18, #60] <------- loading &pc->pc_cpuid > ... > > A (the?) problem is that the compiler is treating "pc" as an alias > for x18, but the rmlock code assumes that the pcpu pointer is loaded > once, as it dereferences "pc" outside of the critical section. On > arm64, if a context switch occurs between the store at _rm_rlock+144 and > the load at +152, and the thread is migrated to another CPU, then we'll > end up using the wrong CPU ID in the rm->rm_writecpus test. > > I suspect the problem is unique to arm64 as its get_pcpu() > implementation is different from the others in that it doesn't use > volatile-qualified inline assembly. This has been the case since > https://cgit.freebsd.org/src/commit/?id=63c858a04d56529eddbddf85ad04fc8e99e73762 > . > > I haven't been able to reproduce any crashes running poudriere in an > arm64 AWS instance, though. Could you please try the patch below and > confirm whether it fixes your panics? I verified that the apparent > problem described above is gone with the patch. > > diff --git a/sys/kern/kern_rmlock.c b/sys/kern/kern_rmlock.c > index 0cdcfb8fec62..e51c25136ae0 100644 > --- a/sys/kern/kern_rmlock.c > +++ b/sys/kern/kern_rmlock.c > @@ -437,6 +437,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock) > { > struct thread *td = curthread; > struct pcpu *pc; > + int cpuid; > > if (SCHEDULER_STOPPED()) > return (1); > @@ -452,6 +453,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock) > atomic_interrupt_fence(); > > pc = get_pcpu(); > + cpuid = pc->pc_cpuid; > rm_tracker_add(pc, tracker); > sched_pin(); > > @@ -463,7 +465,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock) > * conditional jump. > */ > if (__predict_true(0 == (td->td_owepreempt | > - CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)))) > + CPU_ISSET(cpuid, &rm->rm_writecpus)))) > return (1); > > /* We do not have a read token and need to acquire one. */ > > > Hi, This patch paniced again: x0: ffffa00005a31500 x1: ffffa00005a0e000 x2: 2 x3: ffffa00076c4e9a0 x4: 0 x5: e672743c8f9e5 x6: dc89f70500ab1 x7: 14 x8: ffffa00005a31518 x9: 1 x10: ffffa00005a0e000 x11: 0 x12: 0 x13: a x14: 1013e6b85a8ecbe4 x15: 1dce740d11a5 x16: ffff3ea86e2434bf x17: fffffffffffffff2 x18: ffff0000fe661800 (g_ctx + fcf9fa54) x19: ffffa00076c4e9a0 x20: ffff0000fec39000 (g_ctx + fd577254) x21: 2 x22: ffff0000419b6090 (g_ctx + 402f42e4) x23: ffff000000c0b137 (lockstat_enabled + 0) x24: 100 x25: ffff000000c0b000 (version + a0) x26: ffff000000c0b000 (version + a0) x27: ffff000000c0b000 (version + a0) x28: 0 x29: ffff0000fe661800 (g_ctx + fcf9fa54) sp: ffff0000fe661800 lr: ffff00000154ea50 (zio_dva_throttle + 154) elr: ffff00000154ea80 (zio_dva_throttle + 184) spsr: 60000045 far: 2b753286b0b8 panic: Unknown kernel exception 0 esr_el1 2000000 cpuid = 1 time = 1646685857 KDB: stack backtrace: db_trace_self() at db_trace_self db_trace_self_wrapper() at db_trace_self_wrapper+0x30 vpanic() at vpanic+0x174 panic() at panic+0x44 do_el1h_sync() at do_el1h_sync+0x184 handle_el1h_sync() at handle_el1h_sync+0x10 --- exception, esr 0x2000000 zio_dva_throttle() at zio_dva_throttle+0x184 zio_execute() at zio_execute+0x58 KDB: enter: panic [ thread pid 0 tid 100129 ] Stopped at kdb_enter+0x44: undefined f901c11f db> Will try the patch of Andrew next. Compilation might take a while so maybe it wil be tomorrow. Regards, Ronald. ------=_Part_172_1254189170.1646686466401 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit  

Van: Mark Johnston <markj@freebsd.org>
Datum: maandag, 7 maart 2022 16:13
Aan: Ronald Klop <ronald-lists@klop.ws>
CC: bob prohaska <fbsd@www.zefox.net>, Mark Millard <marklmi@yahoo.com>, freebsd-arm@freebsd.org, freebsd-current <freebsd-current@freebsd.org>
Onderwerp: Re: panic: data abort in critical section or under mutex (was: Re: panic: Unknown kernel exception 0 esr_el1 2000000 (on 14-CURRENT/aarch64 Feb 28))

On Mon, Mar 07, 2022 at 02:46:09PM +0100, Ronald Klop wrote:
> Dear Mark Johnston,
>
> I did some binary search in the kernels and came to the conclusion that https://cgit.freebsd.org/src/commit/?id=1517b8d5a7f58897200497811de1b18809c07d3e still works and https://cgit.freebsd.org/src/commit/?id=407c34e735b5d17e2be574808a09e6d729b0a45a panics.
>
> I suspect your commit in https://cgit.freebsd.org/src/commit/?id=c84bb8cd771ce4bed58152e47a32dda470bef23a.
>
> Last panic:
>
> panic: vm_fault failed: ffff00000046e708 error 1
> cpuid = 1
> time = 1646660058
> KDB: stack backtrace:
> db_trace_self() at db_trace_self
> db_trace_self_wrapper() at db_trace_self_wrapper+0x30
> vpanic() at vpanic+0x174
> panic() at panic+0x44
> data_abort() at data_abort+0x2e8
> handle_el1h_sync() at handle_el1h_sync+0x10
> --- exception, esr 0x96000004
> _rm_rlock_debug() at _rm_rlock_debug+0x8c
> osd_get() at osd_get+0x5c
> zio_execute() at zio_execute+0xf8
> taskqueue_run_locked() at taskqueue_run_locked+0x178
> taskqueue_thread_loop() at taskqueue_thread_loop+0xc8
> fork_exit() at fork_exit+0x74
> fork_trampoline() at fork_trampoline+0x14
> KDB: enter: panic
> [ thread pid 0 tid 100129 ]
> Stopped at      kdb_enter+0x44: undefined       f902011f
> db>
>
> A more recent kernel (912df91) still panics. See below.
>
> Do you have time to look into this? What can I provide in information to help?

Hmm.  So after my rmlock commits, we have the following disassembly for
_rm_rlock() (with a few annotations added by me).  Note that the pcpu
pointer is stored in register x18 by convention.

   0xffff00000046e304 <+0>:     stp     x29, x30, [sp, #-16]!
   0xffff00000046e308 <+4>:     mov     x29, sp
   0xffff00000046e30c <+8>:     ldr     x8, [x18]
   0xffff00000046e310 <+12>:    ldr     x9, [x18]
   0xffff00000046e314 <+16>:    ldr     x10, [x18]
   0xffff00000046e318 <+20>:    cmp     x9, x10
   0xffff00000046e31c <+24>:    b.ne    0xffff00000046e3cc <_rm_rlock+200>  // b.any
   0xffff00000046e320 <+28>:    ldr     x9, [x18]
   0xffff00000046e324 <+32>:    ldrh    w9, [x9, #314]
   0xffff00000046e328 <+36>:    cbnz    w9, 0xffff00000046e3c0 <_rm_rlock+188>
   0xffff00000046e32c <+40>:    str     wzr, [x1, #32]
   0xffff00000046e330 <+44>:    stp     x0, x8, [x1, #16]
   0xffff00000046e334 <+48>:    ldrb    w9, [x0, #10]
   0xffff00000046e338 <+52>:    tbz     w9, #4, 0xffff00000046e358 <_rm_rlock+84>
   0xffff00000046e33c <+56>:    ldr     x9, [x18]
   0xffff00000046e340 <+60>:    ldr     w10, [x9, #888]
   0xffff00000046e344 <+64>:    add     w10, w10, #0x1
   0xffff00000046e348 <+68>:    str     w10, [x9, #888]
   0xffff00000046e34c <+72>:    ldr     x9, [x18]
   0xffff00000046e350 <+76>:    ldr     w9, [x9, #888]
   0xffff00000046e354 <+80>:    cbz     w9, 0xffff00000046e3f4 <_rm_rlock+240>
   0xffff00000046e358 <+84>:    ldr     w9, [x8, #1212]
   0xffff00000046e35c <+88>:    add     x10, x18, #0x90
   0xffff00000046e360 <+92>:    add     w9, w9, #0x1
   0xffff00000046e364 <+96>:    str     w9, [x8, #1212]  <------- critical_enter
   0xffff00000046e368 <+100>:   str     x10, [x1, #8]
   0xffff00000046e36c <+104>:   ldr     x9, [x18, #144]
   0xffff00000046e370 <+108>:   str     x9, [x1]
   0xffff00000046e374 <+112>:   str     x1, [x9, #8]
   0xffff00000046e378 <+116>:   str     x1, [x18, #144]
   0xffff00000046e37c <+120>:   ldr     x9, [x18]
   0xffff00000046e380 <+124>:   ldr     w10, [x9, #356]
   0xffff00000046e384 <+128>:   add     w10, w10, #0x1
   0xffff00000046e388 <+132>:   str     w10, [x9, #356]
   0xffff00000046e38c <+136>:   ldr     w9, [x8, #1212]
   0xffff00000046e390 <+140>:   sub     w9, w9, #0x1
   0xffff00000046e394 <+144>:   str     w9, [x8, #1212]  <------- critical_exit
   0xffff00000046e398 <+148>:   ldrb    w8, [x8, #304]
   0xffff00000046e39c <+152>:   ldr     w9, [x18, #60]   <------- loading &pc->pc_cpuid
   ...

A (the?) problem is that the compiler is treating "pc" as an alias
for x18, but the rmlock code assumes that the pcpu pointer is loaded
once, as it dereferences "pc" outside of the critical section.  On
arm64, if a context switch occurs between the store at _rm_rlock+144 and
the load at +152, and the thread is migrated to another CPU, then we'll
end up using the wrong CPU ID in the rm->rm_writecpus test.

I suspect the problem is unique to arm64 as its get_pcpu()
implementation is different from the others in that it doesn't use
volatile-qualified inline assembly.  This has been the case since
https://cgit.freebsd.org/src/commit/?id=63c858a04d56529eddbddf85ad04fc8e99e73762
.

I haven't been able to reproduce any crashes running poudriere in an
arm64 AWS instance, though.  Could you please try the patch below and
confirm whether it fixes your panics?  I verified that the apparent
problem described above is gone with the patch.

diff --git a/sys/kern/kern_rmlock.c b/sys/kern/kern_rmlock.c
index 0cdcfb8fec62..e51c25136ae0 100644
--- a/sys/kern/kern_rmlock.c
+++ b/sys/kern/kern_rmlock.c
@@ -437,6 +437,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
 {
    struct thread *td = curthread;
    struct pcpu *pc;
+   int cpuid;
 
    if (SCHEDULER_STOPPED())
        return (1);
@@ -452,6 +453,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
    atomic_interrupt_fence();
 
    pc = get_pcpu();
+   cpuid = pc->pc_cpuid;
    rm_tracker_add(pc, tracker);
    sched_pin();
 
@@ -463,7 +465,7 @@ _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
     * conditional jump.
     */
    if (__predict_true(0 == (td->td_owepreempt |
-       CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus))))
+       CPU_ISSET(cpuid, &rm->rm_writecpus))))
        return (1);
 
    /* We do not have a read token and need to acquire one. */

Hi,

This patch paniced again: 
x0: ffffa00005a31500                                                                                             
  x1: ffffa00005a0e000                                                                                                            
  x2:                2                                                                                                            
  x3: ffffa00076c4e9a0                                                                                                            
  x4:                0                                                                                                            
  x5:    e672743c8f9e5                                                                                                            
  x6:    dc89f70500ab1
  x7:               14
  x8: ffffa00005a31518
  x9:                1
 x10: ffffa00005a0e000
 x11:                0
 x12:                0
 x13:                a
 x14: 1013e6b85a8ecbe4
 x15:     1dce740d11a5
 x16: ffff3ea86e2434bf
 x17: fffffffffffffff2
 x18: ffff0000fe661800 (g_ctx + fcf9fa54)
 x19: ffffa00076c4e9a0
 x20: ffff0000fec39000 (g_ctx + fd577254)
 x21:                2
 x22: ffff0000419b6090 (g_ctx + 402f42e4)
 x23: ffff000000c0b137 (lockstat_enabled + 0)
 x24:              100
 x25: ffff000000c0b000 (version + a0)
 x26: ffff000000c0b000 (version + a0)
 x27: ffff000000c0b000 (version + a0)
 x28:                0
 x29: ffff0000fe661800 (g_ctx + fcf9fa54)
  sp: ffff0000fe661800
  lr: ffff00000154ea50 (zio_dva_throttle + 154)
 elr: ffff00000154ea80 (zio_dva_throttle + 184)
spsr:         60000045
 far:     2b753286b0b8
panic: Unknown kernel exception 0 esr_el1 2000000
cpuid = 1
time = 1646685857
KDB: stack backtrace:
db_trace_self() at db_trace_self
db_trace_self_wrapper() at db_trace_self_wrapper+0x30
vpanic() at vpanic+0x174
panic() at panic+0x44
do_el1h_sync() at do_el1h_sync+0x184
handle_el1h_sync() at handle_el1h_sync+0x10
--- exception, esr 0x2000000
zio_dva_throttle() at zio_dva_throttle+0x184
zio_execute() at zio_execute+0x58
KDB: enter: panic
[ thread pid 0 tid 100129 ]
Stopped at      kdb_enter+0x44: undefined       f901c11f
db>  
Will try the patch of Andrew next. Compilation might take a while so maybe it wil be tomorrow.

Regards,
Ronald.
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