Re: libpager deadlock

[Samuel Thibault]

HEllo,

Sergio Lopez, le Wed 07 Apr 2010 12:43:15 +0200, a écrit :
> El Sat, 27 Mar 2010 00:39:19 +0100
> Samuel Thibault <samuel.thibault@gnu.org> escribió:
> > From times to times, ext2fs deadlocks on the pager->interlock mutex.
> > This is an excerpt of what I could find in the process:
> > 
> > #2  0x08106e59 in memory_object_lock_request ()
> > #3  0x0806fdeb in _pager_lock_object (p=0x81c97b8, offset=0,
> > size=827392, should_return=2, should_flush=0, lock_value=8, sync=0)
> > at /var/tmp/hurd-20090404/./libpager/lock-object.c:68 #4  0x0806da18
> > in pager_sync (p=0x81c97b8, wait=0)
> > at /var/tmp/hurd-20090404/./libpager/pager-sync.c:31 ... #9
> > 0x0805a9ac in periodic_sync (interval=5)
> > at /var/tmp/hurd-20090404/./libdiskfs/sync-interval.c:119
> > 
> > This is the periodic sync, calling memory_object_lock_request() on the
> > pager.  Note that before doing this, _pager_lock_object takes
> > pager->interlock.
> 
> AFAIK, m_o_lock_request is an asynchronous operation, so it should not
> block in any case. Perhaps the cthreads package is behaving weird?

Above #2  0x08106e59 in memory_object_lock_request (), there is
#0  0x080bf22c in mach_msg_trap ()
#1  0x0808666e in mach_msg ()

So it's really hung in the kernel. And indeed, even if from
the interface it would seem like it could be asynchronous,
the memory_object_lock_completed() call is done from the
memory_object_lock_request function itself...

Samuel