Re: panic: Lock filedesc structure not share locked

On Mon, Jul 01, 2013 at 12:23:35AM +0300, Mikolaj Golub wrote:
> On Sun, Jun 30, 2013 at 10:27:57AM +0200, Mateusz Guzik wrote:
> > On Sun, Jun 30, 2013 at 09:41:50AM +0200, Alexander Leidinger wrote:
> > > Hi,
> > > 
> > > with head as of r252381 on amd64, I got the following panic after
> > > starting tmux and creating a 2nd terminal window inside tmux
> > > (ctrl-<tmux_command_character> + c):
> > > ---snip---
> > > panic: Lock filedesc structure not share locked _at_ /space/system/usr_src/sys/kern/kern_descrip.c:3448
> > > 
> > > cpuid = 2
> > > KDB: stack backtrace:
> > > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xffffff839ee566d0
> > > kdb_backtrace() at kdb_backtrace+0x39/frame 0xffffff839ee56780
> > > vpanic() at vpanic+0x126/frame 0xffffff839ee567c0
> > > panic() at panic+0x43/frame 0xffffff839ee56820
> > > _sx_assert() at _sx_assert+0x134/frame 0xffffff839ee56830
> > > _sx_sunlock() at _sx_sunlock+0x46/frame 0xffffff839ee56860
> > > kern_proc_filedesc_out() at kern_proc_filedesc_out+0x420/frame 0xffffff839ee568e0
> > > sysctl_kern_proc_filedesc() at sysctl_kern_proc_filedesc+0x66/frame 0xffffff839ee56950
> > > sysctl_root() at sysctl_root+0x1bd/frame 0xffffff839ee569a0
> > > userland_sysctl() at userland_sysctl+0x192/frame 0xffffff839ee56a40
> > > sys___sysctl() at sys___sysctl+0x74/frame 0xffffff839ee56af0
> > > amd64_syscall() at amd64_syscall+0x23c/frame 0xffffff839ee56bf0
> > > Xfast_syscall() at Xfast_syscall+0xfb/frame 0xffffff839ee56bf0
> > > ---snip---
> > > 
> > 
> > Can you try this (only compile-tested):
> > diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
> > index e760fe5..7aa17cd 100644
> > --- a/sys/kern/kern_descrip.c
> > +++ b/sys/kern/kern_descrip.c
> > _at__at_ -3272,6 +3272,8 _at__at_ export_fd_to_sb(void *data, int type, int fd, int fflags, int refcnt,
> >  		if (efbuf->remainder < kif->kf_structsize) {
> >  			/* Terminate export. */
> >  			efbuf->remainder = 0;
> > +			if (!locked && efbuf->fdp != NULL)
> > +				FILEDESC_SLOCK(efbuf->fdp);
> >  			return (0);
> >  		}
> >  		efbuf->remainder -= kif->kf_structsize;
> > 
> 
> Mateusz, thank you for spotting this lock leakage. Regardless if this
> is the root cause of the reported panic (it looks like it is), this
> fix should be definetly committed. Will you do this?
> 

I think it will be better if you do this and then MFC all commits.

-- 
Mateusz Guzik <mjguzik gmail.com>