tree d757d605cad64e1ca4c2ebe2a9c71fe789797a76
parent 64325a3be08d364a62ee8f84b2cf86934bc2544a
author Liang Li <liang.li@windriver.com> 1358589130 +0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1358726600 -0800

pch_uart: fix a deadlock when pch_uart as console

When we use pch_uart as system console like 'console=ttyPCH0,115200',
then 'send break' to it. We'll encounter the deadlock on a cpu/core,
with interrupts disabled on the core. When we happen to have all irqs
affinity to cpu0 then the deadlock on cpu0 actually deadlock whole
system.

In pch_uart_interrupt, we have spin_lock_irqsave(&priv->lock, flags)
then call pch_uart_err_ir when break is received. Then the call to
dev_err would actually call to pch_console_write then we'll run into
another spin_lock(&priv->lock), with interrupts disabled.

So in the call sequence lead by pch_uart_interrupt, we should be
carefully to call functions that will 'print message to console' only
in case the uart port is not being used as serial console.

Signed-off-by: Liang Li <liang.li@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>