printk: Fix rq->lock vs logbuf_lock unlock lock inversion

commit dbda92d16f8655044e082930e4e9d244b87fde77 upstream.

commit 07354eb1a74d1 ("locking printk: Annotate logbuf_lock as raw")
reintroduced a lock inversion problem which was fixed in commit
0b5e1c5255 ("printk: Release console_sem after logbuf_lock"). This
happened probably when fixing up patch rejects.

Restore the ordering and unlock logbuf_lock before releasing
console_sem.

Signed-off-by: ybu <ybu@qti.qualcomm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/E807E903FE6CBE4D95E420FBFCC273B827413C@nasanexd01h.na.qualcomm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Qiang Huang <h.huangqiang@huawei.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/printk.c b/kernel/printk.c
index e131c46..e39adc1 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -822,9 +822,9 @@ static int console_trylock_for_printk(unsigned int cpu)
                }
        }
        printk_cpu = UINT_MAX;
+       raw_spin_unlock(&logbuf_lock);
        if (wake)
                up(&console_sem);
-       raw_spin_unlock(&logbuf_lock);
        return retval;
 }
 static const char recursion_bug_msg [] =