panic: sleeping in an epoch section

[Mark Johnston]

On Wed, Oct 09, 2019 at 04:18:34PM +0200, Hans Petter Selasky wrote:
> On 2019-10-09 15:56, Mark Johnston wrote:
> > On Wed, Oct 09, 2019 at 10:40:04AM +0200, Hans Petter Selasky wrote:
> >> On 2019-10-09 06:36, Yuri Pankov wrote:
> >>> Tried updating from r353072 to r353334 and getting the following panic
> >>> reproducibly on boot (starting dhclient?):
> >>>
> >>> panic: sleeping in an epoch section
> >>> cpuid = 5
> >>> time = 1570591558
> >>> KDB: stack backtrace:
> >>> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> >>> 0xfffffe00af780140
> >>> vpanic() at vpanic+0x19d/frame 0xfffffe00af780190
> >>> panic() at panic+0x43/frame 0xfffffe00af7801f0
> >>> _sleep() at _sleep+0x463/frame 0xfffffe00af780290
> >>> pause_sbt() at pause_sbt+0x10f/frame 0xfffffe00af7802d0
> >>> e1000_write_phy_reg_mdic() at e1000_write_phy_reg_mdic+0xee/frame
> >>> 0xfffffe00af780310
> >>> e1000_enable_phy_wakeup_reg_access_bm() at
> >>> e1000_enable_phy_wakeup_reg_access_bm+0x2b/frame 0xfffffe00af780330
> >>> e1000_update_mc_addr_list_pch2lan() at
> >>> e1000_update_mc_addr_list_pch2lan+0x3a/frame 0xfffffe00af780370
> >>> em_if_multi_set() at em_if_multi_set+0x1d4/frame 0xfffffe00af7803c0
> >>> iflib_if_ioctl() at iflib_if_ioctl+0x100/frame 0xfffffe00af780430
> >>> if_addmulti() at if_addmulti+0x2af/frame 0xfffffe00af7804d0
> >>> in_joingroup_locked() at in_joingroup_locked+0x235/frame 0xfffffe00af780570
> >>> in_joingroup() at in_joingroup+0x5c/frame 0xfffffe00af7805d0
> >>> in_control() at in_control+0xadf/frame 0xfffffe00af780680
> >>> ifioctl() at ifioctl+0x40f/frame 0xfffffe00af780750
> >>> kern_ioctl() at kern_ioctl+0x295/frame 0xfffffe00af7807b0
> >>> sys_ioctl() at sys_ioctl+0x15d/frame 0xfffffe00af780880
> >>> amd64_syscall() at amd64_syscall+0x2b9/frame 0xfffffe00af7809b0
> >>> fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe00af7809b0
> >>> --- syscall (54, FreeBSD ELF64, sys_ioctl), rip = 0x80048051a, rsp =
> >>> 0x7fffffffe3e8, rbp = 0x7fffffffe430 ---
> >>
> >> The SIOCADDMULTI if_ioctl() is not allowed to sleep, because it can be
> >> called from the fast-path, so this is a bug in e1000 driver. Does the
> >> attached patch workaround the issue?
> > 
> > What fast path are you referring to?  The locking protocol used by the
> > multicast code was changed specifically to allow for sleeps in driver
> > ioctl handlers.
> 
> I recall a long time ago seeing that input packet processing may end up 
> calling if_ioctl's . Things may have changed since then though.

That may be true in general, but I can't see any instances of that
for SIOCADDMULTI or SIOCDELMULTI.  I think we should always permit ioctl
handlers to sleep.  In particular, the panic reported above is a bug in
r353292.