Re: 9.99.40: panic: kernel diagnostic assertion "ci->ci_biglock_count == 0" failed

[Andrew Doran <ad%netbsd.org@localhost>]

Hi Thomas,

On Tue, Jan 21, 2020 at 08:47:44PM +0100, Thomas Klausner wrote:

> During a bulk build (in rust AFAICT), I got a panic with
> panic: kernel diagnostic assertion "ci->ci_biglock_count == 0" failed: file "/usr/src/sys/sys/userret.h", line 88
> 
> That's this one:
> 
> static __inline void
> mi_userret(struct lwp *l)
> {
>         struct cpu_info *ci;
> 
>         KPREEMPT_DISABLE(l);
>         ci = l->l_cpu;
>         KASSERT(l->l_blcnt == 0);
>         KASSERT(ci->ci_biglock_count == 0);
> 
> 
> 
> The backtrace in the crash dump is not very helpful:
> 
> (gdb) bt
> #0  0xffffffff80224315 in cpu_reboot (howto=howto@entry=260, bootstr=bootstr@entry=0x0) at /usr/src/sys/arch/amd64/amd64/machdep.c:720
> #1  0xffffffff809f5ec3 in kern_reboot (howto=howto@entry=260, bootstr=bootstr@entry=0x0) at /usr/src/sys/kern/kern_reboot.c:61
> #2  0xffffffff80a37109 in vpanic (fmt=0xffffffff8135e980 "kernel %sassertion \"%s\" failed: file \"%s\", line %d ", ap=ap@entry=0xffffad0928973f48)
>     at /usr/src/sys/kern/subr_prf.c:336
> #3  0xffffffff80e7b0b3 in kern_assert (fmt=fmt@entry=0xffffffff8135e980 "kernel %sassertion \"%s\" failed: file \"%s\", line %d ")
>     at /usr/src/sys/lib/libkern/kern_assert.c:51
> #4  0xffffffff802568ce in mi_userret (l=0xffffcfc320ca9c00) at /usr/src/sys/sys/userret.h:91
> #5  userret (l=0xffffcfc320ca9c00) at ./machine/userret.h:81
> #6  syscall (frame=<optimized out>) at /usr/src/sys/arch/x86/x86/syscall.c:166
> #7  0xffffffff802096ad in handle_syscall ()

hannken@ supplied me with a repro for this one so I'm going to look into it
tomorrow morning.  syzbot has also run into it recently.

Andrew