Re: [PATCH] MPSAFE/LOOKUP_SHARED cd9660

On 12/9/08, John Baldwin <jhb_at_freebsd.org> wrote:
> On Friday 05 December 2008 04:54:23 pm Paul B. Mahol wrote:
>> On 12/5/08, John Baldwin <jhb_at_freebsd.org> wrote:
>> > On Friday 05 December 2008 03:56:31 pm Paul B. Mahol wrote:
>> >> On 12/5/08, John Baldwin <jhb_at_freebsd.org> wrote:
>> >> > On Thursday 20 November 2008 05:47:28 pm John Baldwin wrote:
>> >> >> On Thursday 20 November 2008 04:30:57 pm Paul B. Mahol wrote:
>> >> >> > On 11/19/08, John Baldwin <jhb_at_freebsd.org> wrote:
>> >> >> > > This is a relatively simple patch to mark cd9660 MPSAFE and
>> >> >> > > enable
>> >> > shared
>> >> >> > > lookups.  The changes to cd9660_lookup() mirror similar changes
>> >> >> > > to
>> >> >> > > ufs_lookup() to use static variables for local data rather than
>> >> >> > > abusing
>> >> >> > > i-node members of the parent directory.  I've done some light
>> >> >> > > testing
>> >> >> > > of
>> >> >> > > this, but not super-strenuous.  This patch also includes simple
>> >> >> > > locking
>> >> >> for
>> >> >> > > the iconv support in the kernel.  That locking uses an sx lock
>> >> >> > > to
>> >> >> serialize
>> >> >> > > open and close of translator tables and the associated refcount.
>> >> >> > > Actual
>> >> >> > > conversions do not need any locks, however as the mount holds a
>> >> > reference
>> >> >> on
>> >> >> > > the table.
>> >> >> > >
>> >> >> > > http://www.FreeBSD.org/~jhb/patches/cd9660_mpsafe.patch
>> >> >> > >
>> >> >> >
>> >> >> > With this patch I'm unable to kldunload libiconv.ko once it is
>> >> >> > loaded.
>> >> >> > And trying to kldunload libiconv.ko will make any next
>> >> >> kldload/kldstat/kldunload
>> >> >> > to fail waiting forever(livelock).
>> >> >> >
>> >> >> > Regression were not encountered while only cd9660.ko were
>> >> >> > kldloaded.
>> >> >>
>> >> >> So this is actually due to a bug in the module code.  If you have
>> >> >> two
>> >> > modules
>> >> >> like this:
>> >> >>
>> >> >> DECLARE_MODULE(foo, SI_SUB_DRIVERS, SI_ORDER_FIRST);
>> >> >> DECLARE_MODULE(bar, SI_SUB_DRIVERS, SI_ORDER_SECOND);
>> >> >>
>> >> >> The SI_* constants ensure that foo's module handler is called before
>> > bar's
>> >> >>
>> >> >> module handler for MOD_LOAD.  However, we don't enforce a reverse
> order
>> >> >> (bar
>> >> >> then foo) for MOD_UNLOAD.  In fact, the order of MOD_UNLOAD events
>> >> >> is
>> >> >> random
>> >> >> and has no relation to the SI_* constants. :(
>> >> >>
>> >> >> What is happening here is that one of the 'bar' modules in
>> >> >> libiconv.ko
>> >> >> is
>> >> >> getting unloaded after 'foo' gets unloaded and using a destroyed
>> >> >> lock
>> > (you
>> >> >>
>> >> >> get a panic if you run with INVARIANTS).
>> >> >
>> >> > So this should now be fixed with this commit.  If you could verify
>> >> > that
>> >> > iconv
>> >> > works ok with the latest kern_module.c I would appreciate it.
>> >> >
>> >> > Author: jhb
>> >> > Date: Fri Dec  5 16:47:30 2008
>> >> > New Revision: 185642
>> >> > URL: http://svn.freebsd.org/changeset/base/185642
>> >> >
>> >> > Log:
>> >> >   When the SYSINIT() to load a module invokes the MOD_LOAD event
>> >> > successfully,
>> >> >   move that module to the head of the associated linker file's list
>> >> > of
>> >> > modules.
>> >> >   The end result is that once all the modules are loaded, they are
>> >> > sorted
>> > in
>> >> >   the reverse of their load order.  This causes the kernel linker to
>> > invoke
>> >> >   the MOD_QUIESCE and MOD_UNLOAD events in the reverse of the order
> that
>> >> >   MOD_LOAD was invoked.  This means that the ordering of MOD_LOAD
> events
>> >> > that
>> >> >   is set by the SI_* paramters to DECLARE_MODULE() are now honored in
>> >> > the
>> >> > same
>> >> >   order they would be for SYSUNINIT() for the MOD_QUIESCE and
> MOD_UNLOAD
>> >> >   events.
>> >> >
>> >> >   MFC after:    1 month
>> >> >
>> >> > --
>> >> > John Baldwin
>> >> >
>> >>
>> >> Yes it works, I tried hard multiple times kldload/kldunload
>> >> {libiconv,cd9660,cd9660_iconv in various order} to livelock/panic it,
>> >> but without success.
>> >>
>> >> FYI following LORs happened:
>> >>
>> >> lock order reversal:
>> >>  1st 0xc4322ce8 isofs (isofs) _at_ /usr/src/sys/kern/vfs_lookup.c:442
>> >>  2nd 0xd7d8d740 bufwait (bufwait) _at_ /usr/src/sys/kern/vfs_bio.c:2443
>> >>  3rd 0xc4322bdc isofs (isofs) _at_
>> >> /usr/src/sys/modules/cd9660/../../fs/cd9660/cd9660_vfsops.c:694
>> >
>> > This LOR should be addressed in the latest cd9660 locking patches.
>> >
>> > --
>> > John Baldwin
>> >
>>
>> Oh, why I did not checked new version?
>>
>> Yes that LOR have gone, but when doing "ll -R" first time on /mnt
>> I got following messages from kernel:
>>
>> RRIP without PX field?             x ~ 50 times.
>>
>> I see you changed LK_EXCLUSIVE to flags, and with MPSAFE ....
>
> The RRIP stuff is all done in cd9660_vget_internal() under an exclusive
> lock.
> It could be a property of the ISO image.  "PX" holds permissions (owner,
> etc.).  Do you get the same messages w/o the patch with the same ISO image /
> CD?
>
> --
> John Baldwin
>

No I do not, but I may try other CDs I have many of them, including FreeBSD one.
If it is irrelevant than it should not be displayed.

-- 
Paul