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Bluetooth: Fix race condition with HCI_RESET flag

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During the HCI init phase a completed request might be the last part of
the setup procedure after which the actual init procedure starts. The
init procedure begins with a call to hci_reset_req() which sets the
HCI_RESET flag. The purpose of this flag is to make us ignore any
updates to ncmd/cmd_cnt as long as we haven't received the command
complete event for the HCI_Reset. There's a potential race with this
however:

	hci_req_cmd_complete(hdev, opcode, status);

	if (ev->ncmd && !test_bit(HCI_RESET, &hdev->flags)) {
		atomic_set(&hdev->cmd_cnt, 1);
		if (!skb_queue_empty(&hdev->cmd_q))
			queue_work(hdev->workqueue, &hdev->cmd_work);
	}

Since the hci_req_cmd_complete() will trigger the completion of the
setup stage, it's possible that hci_reset_req() gets called before we
try to read ev->ncmd and the HCI_RESET flag. Because of this the cmd_cnt
would never be updated and the hci_reset_req() in practice ends up
blocking itself.

This patch fixes the issue by updating cmd_cnt before notifying the
request completion, and then reading it again to determine whether the
cmd_work should be queued or not.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This commit is contained in:
Johan Hedberg 2015-03-28 11:17:36 +02:00 • committed by Marcel Holtmann
commit 600b21507e
1 changed files with 10 additions and 10 deletions
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