On Fri, Jan 12, 2024 at 11:15:05PM +0100, Marco Elver wrote: > + /* > + * Stack traces of size 0 are never saved, and we can simply use > + * the size field as an indicator if this is a new unused stack > + * record in the freelist. > + */ > + stack->size = 0; I would use WRITE_ONCE here too, at least for TSan. > + return NULL; > + > + /* > + * We maintain the invariant that the elements in front are least > + * recently used, and are therefore more likely to be associated with an > + * RCU grace period in the past. Consequently it is sufficient to only > + * check the first entry. > + */ > + stack = list_first_entry(&free_stacks, struct stack_record, free_list); > + if (stack->size && !poll_state_synchronize_rcu(stack->rcu_state)) READ_ONCE (also for TSan, and might be safer long term in case the compiler considers some fancy code transformation) > + return NULL; > > + stack = depot_pop_free(); > + if (WARN_ON(!stack)) Won't you get nesting problems here if this triggers due to the print? I assume the nmi safe printk won't consider it like an NMI. > counters[DEPOT_COUNTER_FREELIST_SIZE]++; > counters[DEPOT_COUNTER_FREES]++; > counters[DEPOT_COUNTER_INUSE]--; > + > + printk_deferred_exit(); Ah this handles the WARN_ON? Should be ok then. -Andi
