On Tue, Feb 06, 2024 at 06:37:05PM +0800, Zhiguo Niu wrote:
hi Greg,
On Sat, Feb 3, 2024 at 5:36 AM Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Feb 02, 2024 at 07:55:48PM +0000, Carlos Llamas wrote:
On Fri, Feb 02, 2024 at 04:14:36PM +0800, Zhiguo Niu wrote:
There is a deadlock scenario between lockdep and rcu when rcu nocb feature is enabled, just as following call stack:
rcuop/x-000|queued_spin_lock_slowpath(lock = 0xFFFFFF817F2A8A80, val = ?) -001|queued_spin_lock(inline) // try to hold nocb_gp_lock -001|do_raw_spin_lock(lock = 0xFFFFFF817F2A8A80) -002|__raw_spin_lock_irqsave(inline) -002|_raw_spin_lock_irqsave(lock = 0xFFFFFF817F2A8A80) -003|wake_nocb_gp_defer(inline) -003|__call_rcu_nocb_wake(rdp = 0xFFFFFF817F30B680) -004|__call_rcu_common(inline) -004|call_rcu(head = 0xFFFFFFC082EECC28, func = ?) -005|call_rcu_zapped(inline) -005|free_zapped_rcu(ch = ?)// hold graph lock -006|rcu_do_batch(rdp = 0xFFFFFF817F245680) -007|nocb_cb_wait(inline) -007|rcu_nocb_cb_kthread(arg = 0xFFFFFF817F245680) -008|kthread(_create = 0xFFFFFF80803122C0) -009|ret_from_fork(asm)
rcuop/y-000|queued_spin_lock_slowpath(lock = 0xFFFFFFC08291BBC8, val = 0) -001|queued_spin_lock() -001|lockdep_lock() -001|graph_lock() // try to hold graph lock -002|lookup_chain_cache_add() -002|validate_chain() -003|lock_acquire -004|_raw_spin_lock_irqsave(lock = 0xFFFFFF817F211D80) -005|lock_timer_base(inline) -006|mod_timer(inline) -006|wake_nocb_gp_defer(inline)// hold nocb_gp_lock -006|__call_rcu_nocb_wake(rdp = 0xFFFFFF817F2A8680) -007|__call_rcu_common(inline) -007|call_rcu(head = 0xFFFFFFC0822E0B58, func = ?) -008|call_rcu_hurry(inline) -008|rcu_sync_call(inline) -008|rcu_sync_func(rhp = 0xFFFFFFC0822E0B58) -009|rcu_do_batch(rdp = 0xFFFFFF817F266680) -010|nocb_cb_wait(inline) -010|rcu_nocb_cb_kthread(arg = 0xFFFFFF817F266680) -011|kthread(_create = 0xFFFFFF8080363740) -012|ret_from_fork(asm)
rcuop/x and rcuop/y are rcu nocb threads with the same nocb gp thread. This patch release the graph lock before lockdep call_rcu.
Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") Cc: stable@vger.kernel.org
Oops, I missed this line ^^^
Cc: Boqun Feng boqun.feng@gmail.com Cc: Waiman Long longman@redhat.com Cc: Carlos Llamas cmllamas@google.com Cc: Bart Van Assche bvanassche@acm.org Signed-off-by: Zhiguo Niu zhiguo.niu@unisoc.com Signed-off-by: Xuewen Yan xuewen.yan@unisoc.com
changes of v3: correct code comments and add Cc tag. changes of v2: update patch according to Boqun's suggestions.
It seems v3 should have collected the review tags from Boqun and Waiman. Also, I'm actually Cc'ing stable here. I hope that is enough. FWIW, this looks fine to me.
Reviewed-by: Carlos Llamas cmllamas@google.com
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
</formletter>
I see that many commits in mainline use Cc: stable@vger.kernel.org directly without other information, and I also find this information from above link: "Note, such tagging is unnecessary if the stable team can derive the appropriate versions from Fixes: tags."
In addition, this fixed commit "a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use")" was committed in 2019, so I am not very sure which start version should be added to stabe tag. Do you have any good suggestions?
Nope, you did this right, I missed it in the body of the changelog as listed above, my apologies for the incorrect response here.
greg k-h