Date: Fri, 7 Dec 2007 12:12:15 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Stefano Brivio <stefano.brivio@polimi.it>, Robert Love <rml@tech9.net>,
       linux-kernel@vger.kernel.org, Dave Jones <davej@redhat.com>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, Michael Buesch <mb@bu3sch.de>,
       Thomas Gleixner <tglx@linutronix.de>, Len Brown <lenb@kernel.org>
Subject: Re: [PATCH] scheduler: fix x86 regression in native_sched_clock
Message-ID: <20071207111215.GA9502@elte.hu>
References: <20071207021952.6f0ac922@morte> <20071207084559.GA11162@elte.hu> <20071207023241.15274ef6.akpm@linux-foundation.org> <20071207104013.GC27307@elte.hu> <20071207030954.8c1fedc5.akpm@linux-foundation.org>
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* Andrew Morton <akpm@linux-foundation.org> wrote:

> > > A bit risky - it's quite an expansion of code which no longer can 
> > > call printk.
> > > 
> > > You might want to take that WARN_ON out of __update_rq_clock() ;)
> > 
> > hm, dont we already detect printk recursions and turn them into a 
> > silent return instead of a hang/crash?
> 
> We'll pop the locks and will proceed to do the nested printk.  So 
> __update_rq_clock() will need rather a lot of stack ;)

yeah. That behavior of printk is rather fragile. I think my previous 
patch should handle all such incidents.

	Ingo
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