linux-kernel - [PATCH 2/3] firewire: core: disable bus management work temporarily during updating topology

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Message-ID: <20250917000347.52369-3-o-takashi@sakamocchi.jp>
Date: Wed, 17 Sep 2025 09:03:46 +0900
From: Takashi Sakamoto <o-takashi@...amocchi.jp>
To: linux1394-devel@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] firewire: core: disable bus management work temporarily during updating topology

When processing selfID sequence, bus topology tree is (re)built, and some
members of fw_card are determined. Once determined, the members are valid
during the bus generation. The above operations are in the critical
section of fw_card spin lock.

Before building the bus topology, a work item is scheduled for bus manager
work. The bm_work() function is invoked by the work item. The function
tries to acquire the spin lock, then can be stalled until the bus topology
building finishes.

The bus manager should work once the members of fw_card are determined.
This commit suppresses the above situation by disabling the work item
during processing selfID sequence.

Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
---
 drivers/firewire/core-topology.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/firewire/core-topology.c b/drivers/firewire/core-topology.c
index 2f73bcd5696f..90b988035a2a 100644
--- a/drivers/firewire/core-topology.c
+++ b/drivers/firewire/core-topology.c
@@ -460,8 +460,14 @@ void fw_core_handle_bus_reset(struct fw_card *card, int node_id, int generation,
 {
 	struct fw_node *local_node;

+	might_sleep();
+
 	trace_bus_reset_handle(card->index, generation, node_id, bm_abdicate, self_ids, self_id_count);

+	// Disable bus management work during updating the cache of bus topology, since the work
+	// accesses to some members of fw_card.
+	disable_delayed_work_sync(&card->bm_work);
+
 	scoped_guard(spinlock, &card->lock) {
 		// If the selfID buffer is not the immediate successor of the
 		// previously processed one, we cannot reliably compare the
@@ -495,6 +501,8 @@ void fw_core_handle_bus_reset(struct fw_card *card, int node_id, int generation,
 		}
 	}

+	enable_delayed_work(&card->bm_work);
+
 	fw_schedule_bm_work(card, 0);

 	// Just used by transaction layer.
-- 
2.48.1