printk: avoid double lock acquire

Commit 4f2a8d3cf5e ("printk: Fix console_sem vs logbuf_lock unlock race")
introduced another silly bug where we would want to acquire an already
held lock.  Avoid this.

Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/printk.c b/kernel/printk.c
index ecdf6816b64438bfd3a51a2c726ece582ae088d7..989e4a52da76e10c6bb43601d1a49931f7bb82ed 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1292,10 +1292,11 @@ again:
        raw_spin_lock(&logbuf_lock);
        if (con_start != log_end)
                retry = 1;
+       raw_spin_unlock_irqrestore(&logbuf_lock, flags);
+
        if (retry && console_trylock())
                goto again;
 
-       raw_spin_unlock_irqrestore(&logbuf_lock, flags);
        if (wake_klogd)
                wake_up_klogd();
 }