tree 3ef33f2508533a2270448a15dc42f62498b0d0d7
parent 129139a26325d2274a226407d1e7b6f1eb40b456
author Leo Yan <leo.yan@linaro.org> 1574864143 +0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1578824657 +0100

tty: serial: msm_serial: Fix lockup for sysrq and oops

commit 0e4f7f920a5c6bfe5e851e989f27b35a0cc7fb7e upstream.

As the commit 677fe555cbfb ("serial: imx: Fix recursive locking bug")
has mentioned the uart driver might cause recursive locking between
normal printing and the kernel debugging facilities (e.g. sysrq and
oops).  In the commit it gave out suggestion for fixing recursive
locking issue: "The solution is to avoid locking in the sysrq case
and trylock in the oops_in_progress case."

This patch follows the suggestion (also used the exactly same code with
other serial drivers, e.g. amba-pl011.c) to fix the recursive locking
issue, this can avoid stuck caused by deadlock and print out log for
sysrq and oops.

Fixes: 04896a77a97b ("msm_serial: serial driver for MSM7K onboard serial peripheral.")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Link: https://lore.kernel.org/r/20191127141544.4277-2-leo.yan@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>