pl011_tx_softirq() currently uses spin_{,un}lock(), which are not
sufficient to inhibit pl011_int() from being triggered by a local
IRQ and trying to re-take the same lock. This can lead to
deadlocks.
This patch uses the _irq() locking variants instead to ensure that
pl011_int() handling for a given port is deferred until any
pl011_tx_softirq() work for that port is complete.
Notes for stable:
This patch fixes an issue that is fixed by the following upstream
commit, which is a more substantial rewrite of the affected code,
fixing multiple, mostly more minor issues:
1e84d22322ceed4767db1e5342c830dd60c8210f
serial/amba-pl011: Refactor and simplify TX FIFO handling
The upstream patch was rejected for stable on the reasonable grounds
that it was too big and complex a patch. The original buggy code was
merged in v4.1, and the rewrite was merged in v4.2, leaving only v4.1
affected.
This patch replaces the 1e84d22, for 4.1.x only.
Fixes: 734745caeb9f serial/amba-pl011: Activate TX IRQ passively
Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
Tested-by: Robin Murphy <robin.murphy@xxxxxxx>
Tested-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.1.x
---
drivers/tty/serial/amba-pl011.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 763eb20..0cc622a 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1360,9 +1360,9 @@ static void pl011_tx_softirq(struct work_struct *work)
struct uart_amba_port *uap =
container_of(dwork, struct uart_amba_port, tx_softirq_work);
- spin_lock(&uap->port.lock);
+ spin_lock_irq(&uap->port.lock);
while (pl011_tx_chars(uap)) ;
- spin_unlock(&uap->port.lock);
+ spin_unlock_irq(&uap->port.lock);
}
static void pl011_tx_irq_seen(struct uart_amba_port *uap)
--
1.7.10.4
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