A recent dma mapping error analysis effort showed that a large precentage of dma_map_single() and dma_map_page() returns are not checked for mapping errors. Reference: https://lkml.org/lkml/2012/8/10/326 Adding support for tracking dma mapping and unmapping errors to help assess the following: When do dma mapping errors get detected? How often do these errors occur? Why don't we see failures related to missing dma mapping error checks? Are they silent failures? Signed-off-by: Shuah Khan <shuah.khan@xxxxxx> --- Documentation/DMA-API.txt | 7 +++++++ lib/dma-debug.c | 26 +++++++++++++++++++++++++- 2 files changed, 32 insertions(+), 1 deletion(-) diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 66bd97a..ee10a11 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -638,6 +638,13 @@ this directory the following files can currently be found: dma-api/error_count This file is read-only and shows the total numbers of errors found. + dma-api/dma_map_errors This file is read-only and shows the total + number of dma mapping errors detected. + + dma-api/dma_unmap_errors + This file is read-only and shows the total + number of invalid dma unmapping attempts. + dma-api/num_errors The number in this file shows how many warnings will be printed to the kernel log before it stops. This number is initialized to diff --git a/lib/dma-debug.c b/lib/dma-debug.c index 66ce414..8596114 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -83,6 +83,10 @@ static u32 global_disable __read_mostly; /* Global error count */ static u32 error_count; +/* dma mapping error counts */ +static u32 dma_map_errors; +static u32 dma_unmap_errors; + /* Global error show enable*/ static u32 show_all_errors __read_mostly; /* Number of errors to show */ @@ -104,6 +108,8 @@ static struct dentry *show_num_errors_dent __read_mostly; static struct dentry *num_free_entries_dent __read_mostly; static struct dentry *min_free_entries_dent __read_mostly; static struct dentry *filter_dent __read_mostly; +static struct dentry *dma_map_errors_dent __read_mostly; +static struct dentry *dma_unmap_errors_dent __read_mostly; /* per-driver filter related state */ @@ -695,6 +701,19 @@ static int dma_debug_fs_init(void) if (!filter_dent) goto out_err; + dma_map_errors_dent = debugfs_create_u32("dma_map_errors", 0444, + dma_debug_dent, + &dma_map_errors); + + if (!dma_map_errors_dent) + goto out_err; + + dma_unmap_errors_dent = debugfs_create_u32("dma_unmap_errors", 0444, + dma_debug_dent, + &dma_unmap_errors); + if (!dma_unmap_errors_dent) + goto out_err; + return 0; out_err: @@ -850,6 +869,7 @@ static void check_unmap(struct dma_debug_entry *ref) unsigned long flags; if (dma_mapping_error(ref->dev, ref->dev_addr)) { + dma_unmap_errors += 1; err_printk(ref->dev, NULL, "DMA-API: device driver tries " "to free an invalid DMA memory address\n"); return; @@ -1022,8 +1042,12 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset, if (unlikely(global_disable)) return; - if (unlikely(dma_mapping_error(dev, dma_addr))) + if (unlikely(dma_mapping_error(dev, dma_addr))) { + dma_map_errors += 1; + err_printk(dev, NULL, + "DMA-API: dma_map_page() returned error\n"); return; + } entry = dma_entry_alloc(); if (!entry) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
