dma-debug: Make leak-like behaviour apparent
Now that we can dynamically allocate DMA debug entries to cope with drivers maintaining excessively large numbers of live mappings, a driver which *does* actually have a bug leaking mappings (and is not unloaded) will no longer trigger the "DMA-API: debugging out of memory - disabling" message until it gets to actual kernel OOM conditions, which means it could go unnoticed for a while. To that end, let's inform the user each time the pool has grown to a multiple of its initial size, which should make it apparent that they either have a leak or might want to increase the preallocation size. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Tested-by: Qian Cai <cai@lca.pw> Signed-off-by: Christoph Hellwig <hch@lst.de>
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@ -747,7 +747,11 @@ driver afterwards. This filter can be disabled or changed later using debugfs.
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When the code disables itself at runtime this is most likely because it ran
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out of dma_debug_entries and was unable to allocate more on-demand. 65536
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entries are preallocated at boot - if this is too low for you boot with
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'dma_debug_entries=<your_desired_number>' to overwrite the default.
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'dma_debug_entries=<your_desired_number>' to overwrite the default. The
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code will print to the kernel log each time it has dynamically allocated
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as many entries as were initially preallocated. This is to indicate that a
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larger preallocation size may be appropriate, or if it happens continually
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that a driver may be leaking mappings.
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::
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@ -691,6 +691,18 @@ static struct dma_debug_entry *__dma_entry_alloc(void)
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return entry;
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}
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void __dma_entry_alloc_check_leak(void)
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{
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u32 tmp = nr_total_entries % nr_prealloc_entries;
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/* Shout each time we tick over some multiple of the initial pool */
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if (tmp < DMA_DEBUG_DYNAMIC_ENTRIES) {
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pr_info("dma_debug_entry pool grown to %u (%u00%%)\n",
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nr_total_entries,
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(nr_total_entries / nr_prealloc_entries));
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}
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}
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/* struct dma_entry allocator
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*
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* The next two functions implement the allocator for
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@ -710,6 +722,7 @@ static struct dma_debug_entry *dma_entry_alloc(void)
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pr_err("debugging out of memory - disabling\n");
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return NULL;
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}
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__dma_entry_alloc_check_leak();
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}
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entry = __dma_entry_alloc();
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