Re: [PATCH] MPSAFE/LOOKUP_SHARED cd9660

On 12/10/08, Paul B. Mahol <onemda_at_gmail.com> wrote:
> 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
s/Yes I do. Its to late here ...

> one.
> If it is irrelevant than it should not be displayed.

-- 
Paul