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

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

On Tue, Jan 21, 2020 at 07:59:35PM +0000, Andrew Doran wrote:

> 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.

This should be fixed now, with the following revisions:

cvs rdiff -u -r1.165 -r1.166 src/sys/kern/kern_lock.c                                                                                                                                                       
cvs rdiff -u -r1.336 -r1.337 src/sys/kern/kern_synch.c  

Cheers,
Andrew