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 <[email protected]>
>
> Reviewed-by: Frederic Weisbecker <[email protected]>
Queued with Joel's and Frederic's Reviewed-by, thank you all!
Thanx, Paul
