Messages in this thread | | | Date | Thu, 6 Feb 2014 13:13:20 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH RFC] slub: do not drop slab_mutex for sysfs_slab_{add,remove} |
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On Thu, 6 Feb 2014, Vladimir Davydov wrote:
> Hmm... IIUC the only function of concern is kobject_uevent() - > everything else called from sysfs_slab_{add,remove} is a mix of kmalloc, > kfree, mutex_lock/unlock - in short, nothing dangerous. There we do > call_usermodehelper(), but we do it with UMH_WAIT_EXEC, which means > "wait for exec only, but not for the process to complete". An exec > shouldn't issue any slab-related stuff AFAIU. At least, I tried to run > the patched kernel with lockdep enabled and got no warnings at all when > getting uevents about adding/removing caches. That's why I started to > doubt whether we really need this lock... > > Please correct me if I'm wrong.
I have had this deadlock a couple of years ago. Sysfs seems to change over time. Not sure if that is still the case.
> > I would be very thankful, if you can get that actually working reliably > > without deadlock issues. > > If there is no choice rather than moving sysfs_slab_{add,remove} out of > the slab_mutex critical section, I'll have to do it that way. But first > I'd like to make sure it cannot be done with less footprint.
I am all for holding the lock as long as possible.
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