linux-kernel - Re: [2.6.18-rc7] printk output delay in syslog wrt dmesg still unfixed

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Date:	Fri, 22 Sep 2006 01:28:24 +0200
From:	Tilman Schmidt <tilman@...p.cc>
To:	linux-kernel@...r.kernel.org
CC:	john stultz <johnstul@...ibm.com>
Subject: Re: [2.6.18-rc7] printk output delay in syslog wrt dmesg still unfixed

On 19.09.2006 20:52, john stultz wrote:
> You might try git-bisect to find the offending patch.

This turned out to be easier than I expected.
The patch which introduces the problem is:

[a0f1ccfd8d37457a6d8a9e01acebeefcdfcc306e] lockdep: do not recurse in printk

Reverting that patch makes the problem disappear in 2.6.18, too.
In fact, it suffices to revert just the last chunk:

@@ -809,8 +815,15 @@ void release_console_sem(void)
        console_may_schedule = 0;
        up(&console_sem);
        spin_unlock_irqrestore(&logbuf_lock, flags);
-       if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
-               wake_up_interruptible(&log_wait);
+       if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {
+               /*
+                * If we printk from within the lock dependency code,
+                * from within the scheduler code, then do not lock
+                * up due to self-recursion:
+                */
+               if (!lockdep_internal())
+                       wake_up_interruptible(&log_wait);
+       }
 }
 EXPORT_SYMBOL(release_console_sem);

Hope that helps.

-- 
Tilman Schmidt                          E-Mail: tilman@...p.cc
Bonn, Germany
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