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Date: Thu, 1 Nov 2007 22:11:53 +0100 From: Pavel Machek <pavel@....cz> To: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> Cc: Tim Bird <tim.bird@...sony.com>, Matt Mackall <mpm@...enic.com>, linux kernel <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>, Jon Smirl <jonsmirl@...oo.com> Subject: Re: IRQ off latency of printk is very high Hi! > > > It seems draconian to drain the entire buffer with ints disabled. > > > Is it possible to break this up and send out smaller chunks > > > at a time? Maybe by putting a chunk loop in release_console_sem()? > > > > Well, I believe someone got > > > > DDetetccctted ed 113223 HHzz CPUCPU > > > > in his dmesg, and now we have this 'draconian' locking. How can we > > prevent mangled messages without it? > > The main interest seems to be to protect from mixed printk output > between different CPUs in process context. I don't think it would be > that bad if interrupts come and output error messages in the middle of a > printk, isn't it ? > > therefore, could we do something like : > > > if (!in_irq()) > spin_lock(&logbuf_lock); > ... > if (!in_irq()) > spin_unlock(&logbuf_lock); > > ? (yes, this is a crazy idea) Two messages in atomic sections on different cpus could still be mixed :-). But yes, something like this may be the way to go. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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