pch_uart: fix a deadlock when pch_uart as console
authorLiang Li <liang.li@windriver.com>
Sat, 19 Jan 2013 09:52:10 +0000 (17:52 +0800)
committerBen Hutchings <ben@decadent.org.uk>
Sat, 27 Jul 2013 04:34:33 +0000 (05:34 +0100)
commit790e332c473eded2396dcf7e2902cbe4429b6a80
treeff710918d210e3aca26da8f4f9fced7832e9381c
parent2487f0db30527032c4d56fc2d0b1a240fe89fef8
pch_uart: fix a deadlock when pch_uart as console

commit 384e301e3519599b000c1a2ecd938b533fc15d85 upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
drivers/tty/serial/pch_uart.c