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 <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/kernel/printk.c b/kernel/printk.c
index 1455a0d4eedd4b386c759d689f939ba5d7a9007a..7982a0a841eaf082fe929e24a1f4bd5aefd4f015 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1293,10 +1293,11 @@ 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();
 }