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Message-Id: <1249301157.2893.11.camel@achroite> Date: Mon, 03 Aug 2009 13:05:57 +0100 From: Ben Hutchings <bhutchings@...arflare.com> To: David Miller <davem@...emloft.net> Cc: herbert@...dor.apana.org.au, mpm@...enic.com, netdev@...r.kernel.org, mcarlson@...adcom.com Subject: Re: netpoll + xmit_lock == deadlock On Sun, 2009-08-02 at 13:07 -0700, David Miller wrote: > From: Herbert Xu <herbert@...dor.apana.org.au> > Date: Wed, 29 Jul 2009 15:35:23 +0800 > > > So if a driver is in the TX path, and a printk occurs, then a > > recursive dead lock can occur if that driver tries to take the > > xmit lock in its poll function to clean up descriptors. > > My position has always been that such printk's are simply > not allowed. (check archives if you don't believe me :-) > > The locking is going to get rediculious if we start having > to account for this. I agree with that, but this does seem quite restrictive. How can we be sure that none of the kernel functions used by a driver's TX path (e.g. kmalloc or DMA-mapping) will print debug or warning messages? If such guarantees exist, they do not seem to be documented. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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