From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from SHSQR01.spreadtrum.com (mx1.unisoc.com [222.66.158.135]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2D3E0C8C2 for ; Mon, 15 Jan 2024 08:55:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=unisoc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=unisoc.com Received: from SHSQR01.spreadtrum.com (localhost [127.0.0.2] (may be forged)) by SHSQR01.spreadtrum.com with ESMTP id 40F8t014047556 for ; Mon, 15 Jan 2024 16:55:00 +0800 (+08) (envelope-from Zhiguo.Niu@unisoc.com) Received: from dlp.unisoc.com ([10.29.3.86]) by SHSQR01.spreadtrum.com with ESMTP id 40F8rkXH042583; Mon, 15 Jan 2024 16:53:46 +0800 (+08) (envelope-from Zhiguo.Niu@unisoc.com) Received: from SHDLP.spreadtrum.com (bjmbx02.spreadtrum.com [10.0.64.8]) by dlp.unisoc.com (SkyGuard) with ESMTPS id 4TD5NJ1vNzz2RCYp0; Mon, 15 Jan 2024 16:46:40 +0800 (CST) Received: from bj08434pcu.spreadtrum.com (10.0.73.87) by BJMBX02.spreadtrum.com (10.0.64.8) with Microsoft SMTP Server (TLS) id 15.0.1497.23; Mon, 15 Jan 2024 16:53:44 +0800 From: Zhiguo Niu To: , , , , CC: , , , , Subject: [PATCH] lockdep: fix deadlock issue between lockdep and rcu Date: Mon, 15 Jan 2024 16:53:16 +0800 Message-ID: <1705308796-13547-1-git-send-email-zhiguo.niu@unisoc.com> X-Mailer: git-send-email 1.9.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-ClientProxiedBy: SHCAS01.spreadtrum.com (10.0.1.201) To BJMBX02.spreadtrum.com (10.0.64.8) X-MAIL:SHSQR01.spreadtrum.com 40F8rkXH042583 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. Signed-off-by: Zhiguo Niu Signed-off-by: Xuewen Yan --- kernel/locking/lockdep.c | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 151bd3d..c1d432a 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -6186,23 +6186,29 @@ static struct pending_free *get_pending_free(void) /* * Schedule an RCU callback if no RCU callback is pending. Must be called with * the graph lock held. + * + * Return true if graph lock need be released by the caller, otherwise false + * means graph lock is released by itself. */ -static void call_rcu_zapped(struct pending_free *pf) +static bool call_rcu_zapped(struct pending_free *pf) { WARN_ON_ONCE(inside_selftest()); if (list_empty(&pf->zapped)) - return; + return true; if (delayed_free.scheduled) - return; + return true; delayed_free.scheduled = true; WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf); delayed_free.index ^= 1; + lockdep_unlock(); call_rcu(&delayed_free.rcu_head, free_zapped_rcu); + + return false; } /* The caller must hold the graph lock. May be called from RCU context. */ @@ -6228,6 +6234,7 @@ static void free_zapped_rcu(struct rcu_head *ch) { struct pending_free *pf; unsigned long flags; + bool need_unlock; if (WARN_ON_ONCE(ch != &delayed_free.rcu_head)) return; @@ -6243,9 +6250,9 @@ static void free_zapped_rcu(struct rcu_head *ch) /* * If there's anything on the open list, close and start a new callback. */ - call_rcu_zapped(delayed_free.pf + delayed_free.index); - - lockdep_unlock(); + need_unlock = call_rcu_zapped(delayed_free.pf + delayed_free.index); + if (need_unlock) + 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_unlock; init_data_structures_once(); @@ -6293,8 +6301,9 @@ 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); - lockdep_unlock(); + need_unlock = call_rcu_zapped(pf); + if (need_unlock) + lockdep_unlock(); raw_local_irq_restore(flags); /* @@ -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_unlock; raw_local_irq_save(flags); locked = graph_lock(); @@ -6398,9 +6408,9 @@ static void lockdep_reset_lock_reg(struct lockdep_map *lock) pf = get_pending_free(); __lockdep_reset_lock(pf, lock); - call_rcu_zapped(pf); - - graph_unlock(); + need_unlock = call_rcu_zapped(pf); + if (need_unlock) + graph_unlock(); out_irq: raw_local_irq_restore(flags); } @@ -6446,6 +6456,7 @@ void lockdep_unregister_key(struct lock_class_key *key) struct pending_free *pf; unsigned long flags; bool found = false; + bool need_unlock = true; might_sleep(); @@ -6466,9 +6477,10 @@ 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_unlock = call_rcu_zapped(pf); } - lockdep_unlock(); + if (need_unlock) + lockdep_unlock(); raw_local_irq_restore(flags); /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */ -- 1.9.1