Re: panic: Lock filedesc structure not share locked

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 Guzik <mjguzik gmail.com>