gcc-4.6: printk: use stable variable to dump kmsg buffer

kmsg_dump takes care to sample the global variables
inside a spinlock, but then goes on to use the same
variables outside the spinlock region too.

Use the correct variable. This will make the race
window smaller.

Found by gcc 4.6's new warnings.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/printk.c b/kernel/printk.c
index 4ab0164..8fe465a 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1549,9 +1549,9 @@ void kmsg_dump(enum kmsg_dump_reason reason)
        chars = logged_chars;
        spin_unlock_irqrestore(&logbuf_lock, flags);
 
-       if (logged_chars > end) {
-               s1 = log_buf + log_buf_len - logged_chars + end;
-               l1 = logged_chars - end;
+       if (chars > end) {
+               s1 = log_buf + log_buf_len - chars + end;
+               l1 = chars - end;
 
                s2 = log_buf;
                l2 = end;
@@ -1559,8 +1559,8 @@ void kmsg_dump(enum kmsg_dump_reason reason)
                s1 = "";
                l1 = 0;
 
-               s2 = log_buf + end - logged_chars;
-               l2 = logged_chars;
+               s2 = log_buf + end - chars;
+               l2 = chars;
        }
 
        if (!spin_trylock_irqsave(&dump_list_lock, flags)) {