linux-kernel - [patch 2/4] firewire: fully initialize fw_transaction before marking it pending

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Date:	Sat, 12 Jul 2008 14:50:06 +0200 (CEST)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	linux-kernel@...r.kernel.org
Subject: [patch 2/4] firewire: fully initialize fw_transaction before marking
 it pending

In theory, card->flush_timer could already access a transaction between
fw_send_request()'s spin_unlock_irqrestore and the rest of what happens
in fw_send_request().  This would happen if the process which sends the
request is preempted and put to sleep right after spin_unlock_irqrestore
for longer than 100ms.

Therefore we fill in everything in struct fw_transaction at which the
flush_timer might look at before we lift the lock.

To do:  Ensure that the timer does not pick up the transaction before
the time of the AT request event plus split transaction timeout.

Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
 drivers/firewire/fw-transaction.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

Index: linux/drivers/firewire/fw-transaction.c
===================================================================
--- linux.orig/drivers/firewire/fw-transaction.c
+++ linux/drivers/firewire/fw-transaction.c
@@ -279,11 +279,6 @@ fw_send_request(struct fw_card *card, st
 	card->current_tlabel = (card->current_tlabel + 1) & 0x1f;
 	card->tlabel_mask |= (1 << tlabel);
 
-	list_add_tail(&t->link, &card->transaction_list);
-
-	spin_unlock_irqrestore(&card->lock, flags);
-
-	/* Initialize rest of transaction, fill out packet and send it. */
 	t->node_id = node_id;
 	t->tlabel = tlabel;
 	t->callback = callback;
@@ -294,6 +289,10 @@ fw_send_request(struct fw_card *card, st
 			speed, offset, payload, length);
 	t->packet.callback = transmit_complete_callback;
 
+	list_add_tail(&t->link, &card->transaction_list);
+
+	spin_unlock_irqrestore(&card->lock, flags);
+
 	card->driver->send_request(card, &t->packet);
 }
 EXPORT_SYMBOL(fw_send_request);

-- 
Stefan Richter
-=====-==--- -=== -==--
http://arcgraph.de/sr/

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