From: liu chuansheng <chuansheng.liu@intel.com>
Date: Fri, 6 Jul 2012 16:50:08 +0000 (-0700)
Subject: printk: replacing the raw_spin_lock/unlock with raw_spin_lock/unlock_irq
X-Git-Tag: v3.5-rc7~29^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5c53d819c71c63fdc91f30a59164583f68e2d63a;p=pandora-kernel.git

printk: replacing the raw_spin_lock/unlock with raw_spin_lock/unlock_irq

In function devkmsg_read/writev/llseek/poll/open()..., the function
raw_spin_lock/unlock is used, there is potential deadlock case happening.
CPU1: thread1 doing the cat /dev/kmsg:
        raw_spin_lock(&logbuf_lock);
        while (user->seq == log_next_seq) {
when thread1 run here, at this time one interrupt is coming on CPU1 and running
based on this thread,if the interrupt handle called the printk which need the
logbuf_lock spin also, it will cause deadlock.

So we should use raw_spin_lock/unlock_irq here.

Acked-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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