On Thu, Jun 20, 2024 at 10:54:34PM +0000, Carlos Llamas wrote:
From: Zhiguo Niu zhiguo.niu@unisoc.com
There is a deadlock scenario between lockdep and rcu when rcu nocb feature is enabled, just as following call stack:
I have pulled this into -rcu for further review and testing.
If someone else (for example, the lockdep folks) would like to take this:
Acked-by: Paul E. McKenney paulmck@kernel.org
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 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 Reviewed-by: Boqun Feng boqun.feng@gmail.com Reviewed-by: Waiman Long longman@redhat.com Reviewed-by: Carlos Llamas cmllamas@google.com Reviewed-by: Bart Van Assche bvanassche@acm.org Signed-off-by: Carlos Llamas cmllamas@google.com
kernel/locking/lockdep.c | 48 ++++++++++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 16 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 151bd3de5936..3468d8230e5f 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -6184,25 +6184,27 @@ static struct pending_free *get_pending_free(void) static void free_zapped_rcu(struct rcu_head *cb); /*
- Schedule an RCU callback if no RCU callback is pending. Must be called with
- the graph lock held.
- */
-static void call_rcu_zapped(struct pending_free *pf) +* See if we need to queue an RCU callback, must called with +* the lockdep lock held, returns false if either we don't have +* any pending free or the callback is already scheduled. +* Otherwise, a call_rcu() must follow this function call. +*/ +static bool prepare_call_rcu_zapped(struct pending_free *pf) { WARN_ON_ONCE(inside_selftest()); if (list_empty(&pf->zapped))
return;
return false;if (delayed_free.scheduled)
return;
return false;delayed_free.scheduled = true; WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf); delayed_free.index ^= 1;
- call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
- return true;
} /* The caller must hold the graph lock. May be called from RCU context. */ @@ -6228,6 +6230,7 @@ static void free_zapped_rcu(struct rcu_head *ch) { struct pending_free *pf; unsigned long flags;
- bool need_callback;
if (WARN_ON_ONCE(ch != &delayed_free.rcu_head)) return; @@ -6239,14 +6242,18 @@ static void free_zapped_rcu(struct rcu_head *ch) pf = delayed_free.pf + (delayed_free.index ^ 1); __free_zapped_classes(pf); delayed_free.scheduled = false;
- need_callback =
prepare_call_rcu_zapped(delayed_free.pf + delayed_free.index);- lockdep_unlock();
- raw_local_irq_restore(flags);
/*
* If there's anything on the open list, close and start a new callback.*/- call_rcu_zapped(delayed_free.pf + delayed_free.index);
- If there's pending free and its callback has not been scheduled,
- queue an RCU callback.
- */
- if (need_callback)
call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
- lockdep_unlock();
- raw_local_irq_restore(flags);
} /* @@ -6286,6 +6293,7 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size) { struct pending_free *pf; unsigned long flags;
- bool need_callback;
init_data_structures_once(); @@ -6293,10 +6301,11 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size) lockdep_lock(); pf = get_pending_free(); __lockdep_free_key_range(pf, start, size);
- call_rcu_zapped(pf);
- need_callback = prepare_call_rcu_zapped(pf); lockdep_unlock(); raw_local_irq_restore(flags);
- if (need_callback)
call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
- Wait for any possible iterators from look_up_lock_class() to pass
- before continuing to free the memory they refer to.
@@ -6390,6 +6399,7 @@ static void lockdep_reset_lock_reg(struct lockdep_map *lock) struct pending_free *pf; unsigned long flags; int locked;
- bool need_callback = false;
raw_local_irq_save(flags); locked = graph_lock(); @@ -6398,11 +6408,13 @@ static void lockdep_reset_lock_reg(struct lockdep_map *lock) pf = get_pending_free(); __lockdep_reset_lock(pf, lock);
- call_rcu_zapped(pf);
- need_callback = prepare_call_rcu_zapped(pf);
graph_unlock(); out_irq: raw_local_irq_restore(flags);
- if (need_callback)
call_rcu(&delayed_free.rcu_head, free_zapped_rcu);} /* @@ -6446,6 +6458,7 @@ void lockdep_unregister_key(struct lock_class_key *key) struct pending_free *pf; unsigned long flags; bool found = false;
- bool need_callback = false;
might_sleep(); @@ -6466,11 +6479,14 @@ void lockdep_unregister_key(struct lock_class_key *key) if (found) { pf = get_pending_free(); __lockdep_free_key_range(pf, key, 1);
call_rcu_zapped(pf);
need_callback = prepare_call_rcu_zapped(pf);
- if (need_callback)
call_rcu(&delayed_free.rcu_head, free_zapped_rcu);- /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */ synchronize_rcu();
}
2.45.2.741.gdbec12cfda-goog