> In 32bit SMP systems, if the system is stressed on the sys node > by processes, it may cause blkcg_fill_root_iostats to have a concurrent > problem on the seqlock in u64_stats_update, which will cause a deadlock > on u64_stats_fetch_begin in blkcg_print_one_stat. Would you like to mark any references to functions with parentheses? > To prevent this problem, add spin_locks. Another wording suggestion: Thus use an additional spin lock. How do you think about to use a summary phrase like “Add a spin lock for stats update in blkcg_fill_root_iostats()”? … > +++ b/block/blk-cgroup.c > @@ -1134,9 +1134,15 @@ static void blkcg_fill_root_iostats(void) > cpu_dkstats->sectors[STAT_DISCARD] << 9; > } > > +#if BITS_PER_LONG == 32 > + spin_lock_irq(&blkg->q->queue_lock); > +#endif > flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync); > blkg_iostat_set(&blkg->iostat.cur, &tmp); > u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags); > +#if BITS_PER_LONG == 32 > + spin_unlock_irq(&blkg->q->queue_lock); > +#endif … Under which circumstances would you become interested to apply a statement like “guard(spinlock_irq)(&blkg->q->queue_lock);”? https://elixir.bootlin.com/linux/v6.10-rc6/source/include/linux/spinlock.h#L567 Regards, Markus
