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Date: Mon, 16 May 2011 13:00:29 +0200
From: "Roedel, Joerg" <Joerg.Roedel@amd.com>
To: Johannes Berg <johannes@sipsolutions.net>
CC: linux-kernel <linux-kernel@vger.kernel.org>,
        David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v2] dma-debug: print some unfreed allocations
Message-ID: <20110516110029.GC31309@amd.com>
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On Wed, May 11, 2011 at 08:47:57AM -0400, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>

> +#ifdef CONFIG_STACKTRACE
> +		count = 0;
> +		/*
> +		 * If we have, print out some stack traces for the allocations.
> +		 * In case of module unload, the stack traces will be useless,
> +		 * but instead of unloading the module you can manually unbind
> +		 * the driver instead and get useful traces.
> +		 */
> +		printk(KERN_WARNING "Showing traces for %d allocations:\n",
> +		       DMA_DEBUG_NUM_PRINT_UNFREED);
> +
> +		for (i = 0; i < HASH_SIZE; ++i) {
> +			spin_lock(&dma_entry_hash[i].lock);
> +			list_for_each_entry(entry, &dma_entry_hash[i].list,
> +					    list) {
> +				if (entry->dev != dev)
> +					continue;
> +				count += 1;
> +				if (count > DMA_DEBUG_NUM_PRINT_UNFREED)
> +					break;
> +				dump_entry_trace(entry);
> +			}
> +			spin_unlock(&dma_entry_hash[i].lock);
>  
> -	return count;
> +			if (count > DMA_DEBUG_NUM_PRINT_UNFREED)
> +				break;
> +		}
> +#endif
> +	}
> +
> +	local_irq_restore(flags);
>  }

This is surely useful to developers, but can trash the dmesg if done
unconditionally. I would prefer this verbose output to be configurable
and off by default.

	Joerg