linux-kernel - [PATCH 3.16 32/47] s390/qdio: don't touch the dsci in tiqdio_add_input

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Message-ID: <lsq.1572026582.890954541@decadent.org.uk>
Date:   Fri, 25 Oct 2019 19:03:33 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Vasily Gorbik" <gor@...ux.ibm.com>,
        "Julian Wiedmann" <jwi@...ux.ibm.com>
Subject: [PATCH 3.16 32/47] s390/qdio: don't touch the dsci in
 tiqdio_add_input_queues()

3.16.76-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Julian Wiedmann <jwi@...ux.ibm.com>

commit ac6639cd3db607d386616487902b4cc1850a7be5 upstream.

Current code sets the dsci to 0x00000080. Which doesn't make any sense,
as the indicator area is located in the _left-most_ byte.

Worse: if the dsci is the _shared_ indicator, this potentially clears
the indication of activity for a _different_ device.
tiqdio_thinint_handler() will then have no reason to call that device's
IRQ handler, and the device ends up stalling.

Fixes: d0c9d4a89fff ("[S390] qdio: set correct bit in dsci")
Signed-off-by: Julian Wiedmann <jwi@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/s390/cio/qdio_thinint.c | 1 -
 1 file changed, 1 deletion(-)

--- a/drivers/s390/cio/qdio_thinint.c
+++ b/drivers/s390/cio/qdio_thinint.c
@@ -80,7 +80,6 @@ void tiqdio_add_input_queues(struct qdio
 	mutex_lock(&tiq_list_lock);
 	list_add_rcu(&irq_ptr->input_qs[0]->entry, &tiq_list);
 	mutex_unlock(&tiq_list_lock);
-	xchg(irq_ptr->dsci, 1 << 7);
 }
 
 void tiqdio_remove_input_queues(struct qdio_irq *irq_ptr)