On Fri, Jan 12, 2024 at 05:09:12PM +0100, Frederic Weisbecker wrote: > 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 <qiang.zhang1211@xxxxxxxxx> > > Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx> Queued with Joel's and Frederic's Reviewed-by, thank you all! Thanx, Paul
