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> On 2/26/26 15:50, Vlastimil Babka (SUSE) wrote: > > On 2/11/26 10:42, Vlastimil Babka wrote: > >> sheaf_flush_main() can be called from __pcs_replace_full_main() where > >> the trylock can in theory fail, and pcs_flush_all() where it's not > >> expected to and it would be actually a problem if it failed and left the > >> main sheaf not flushed. > > > > Thinking about this more, I now think it's not a theoretical issue because > > on PREEMPT_RT I think pcs_flush_all() can preempt someone holding the lock Agreed! > > (on PREEMPT_RT it doesn't have to be an irq handler preempting a holder), > > and then fail to flush the main sheaf silently. > > > > The impact is probably limited though - if this failure to flush happens in > > __kmem_cache_shutdown(), it means someone was destroying a cache while using > > it, so that was already buggy. slab_mem_going_offline_callback() could be > > where this matters although it's unlikely someone would do memory hotplug > > together with PREEMPT_RT. > > > > But maybe still worth tagging this as Fixes: 2d517aa09bbc ("slab: add opt-in > > caching layer of percpu sheaves") and Cc stable and sending it as a hotfix. > > Added to slab/for-next-fixes with adjusted changelog: > > https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/commit/?h=slab*for-next-fixes&id=48647d3f9a644d1e81af6558102d43cdb260597b -- Cheers, Harry / Hyeonggon