On Wed, Jan 10, 2024 at 04:11:28PM +0800, Zqiang wrote: > For the kernels built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and > CONFIG_RCU_LAZY=y, here are the following scenarios that will trigger > WARN_ON_ONCE() in the rcu_nocb_bypass_lock() and rcu_nocb_wait_contended(). > > CPU2 CPU11 > kthread > rcu_nocb_cb_kthread ksys_write > rcu_do_batch vfs_write > rcu_torture_timer_cb proc_sys_write > __kmem_cache_free > proc_sys_call_handler > kmemleak_free > drop_caches_sysctl_handler > delete_object_full drop_slab > __delete_object shrink_slab > put_object lazy_rcu_shrink_scan > call_rcu > rcu_nocb_flush_bypass > __call_rcu_commn > rcu_nocb_bypass_lock > > raw_spin_trylock(&rdp->nocb_bypass_lock) fail > > atomic_inc(&rdp->nocb_lock_contended); > rcu_nocb_wait_contended > WARN_ON_ONCE(smp_processor_id() != rdp->cpu); > WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)) > | > |_ _ _ _ _ _ _ _ _ _same rdp and rdp->cpu != 11_ > _ _ _ _ _ _ _ _ __| > > This commit therefore use the rcu_nocb_try_flush_bypass() instead of > rcu_nocb_flush_bypass() in lazy_rcu_shrink_scan(), if the nocb_bypass > queue is being flushed, the rcu_nocb_try_flush_bypass will return directly. > > Signed-off-by: Zqiang <[email protected]>
Reviewed-by: Frederic Weisbecker <[email protected]>
