On Mon, May 27, 2024 at 06:34:24PM GMT, Vlastimil Babka (SUSE) wrote: > On 5/27/24 5:22 PM, Sebastian Andrzej Siewior wrote: > > On 2024-04-20 16:25:05 [-0700], Shakeel Butt wrote: > >> mod_memcg_lruvec_state() is never called from outside of memcontrol.c > >> and with always irq disabled. So, replace it with the irq disabled > >> version and add an assert that irq is disabled in the caller. > > > > unless PREEMPT_RT is enabled. In that case IRQs are not disabled as part > > of local_lock_irqsave(&memcg_stock.stock_lock, …) leading to: Sorry about that and thanks for the report. > > But then the "interrupts are handled by a kernel thread that can sleep" part > of RT also means it's ok to just have the stock_lock taken with no > interrupts disabled as no actual raw interrupt handler will interrupt the > holder and deadlock, right? > Thanks Vlastimil for jolting my memory on RT reasoning. > > | ------------[ cut here ]------------ > > | WARNING: CPU: 0 PID: 1 at mm/memcontrol.c:3150 __mod_objcg_mlstate+0xc2/0x110 > > | CPU: 0 PID: 1 Comm: systemd Not tainted 6.10.0-rc1-rt0+ #17 > > | Call Trace: > > | <TASK> > > | mod_objcg_state+0x2b3/0x320 > > | __memcg_slab_post_alloc_hook+0x13c/0x340 > > | kmem_cache_alloc_lru_noprof+0x2bd/0x2e0 > > | alloc_inode+0x59/0xc0 > > | iget_locked+0xf0/0x290 > > > > suggestions? > > So in that case the appropriate thing would be to replace the assert with > lockdep_assert_held(&memcg_stock.stock_lock); > ? > > It seems all the code paths leading here have that one. > Yeah this seems right and reasonable. Should I send a fix or you want to send it?
