From: Robin Murphy <robin.murphy@arm.com>
To: hch@lst.de
Cc: m.szyprowski@samsung.com, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, cai@gmx.us, salil.mehta@huawei.com,
john.garry@huawei.com
Subject: [PATCH v3 4/7] dma-debug: Make leak-like behaviour apparent
Date: Mon, 10 Dec 2018 14:00:30 +0000 [thread overview]
Message-ID: <22f6c17167b7270226d30dcd320eaff656a98bd4.1544447601.git.robin.murphy@arm.com> (raw)
In-Reply-To: <cover.1544447601.git.robin.murphy@arm.com>
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.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
v3: Add Christoph's review tag
Documentation/DMA-API.txt | 6 +++++-
kernel/dma/debug.c | 13 +++++++++++++
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 0fcb7561af1e..7a7d8a415ce8 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -747,7 +747,11 @@ driver afterwards. This filter can be disabled or changed later using debugfs.
When the code disables itself at runtime this is most likely because it ran
out of dma_debug_entries and was unable to allocate more on-demand. 65536
entries are preallocated at boot - if this is too low for you boot with
-'dma_debug_entries=<your_desired_number>' to overwrite the default.
+'dma_debug_entries=<your_desired_number>' to overwrite the default. The
+code will print to the kernel log each time it has dynamically allocated
+as many entries as were initially preallocated. This is to indicate that a
+larger preallocation size may be appropriate, or if it happens continually
+that a driver may be leaking mappings.
::
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index ef7c90b7a346..912c23f4c177 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -691,6 +691,18 @@ static struct dma_debug_entry *__dma_entry_alloc(void)
return entry;
}
+void __dma_entry_alloc_check_leak(void)
+{
+ u32 tmp = nr_total_entries % nr_prealloc_entries;
+
+ /* Shout each time we tick over some multiple of the initial pool */
+ if (tmp < DMA_DEBUG_DYNAMIC_ENTRIES) {
+ pr_info("dma_debug_entry pool grown to %u (%u00%%)\n",
+ nr_total_entries,
+ (nr_total_entries / nr_prealloc_entries));
+ }
+}
+
/* struct dma_entry allocator
*
* The next two functions implement the allocator for
@@ -710,6 +722,7 @@ static struct dma_debug_entry *dma_entry_alloc(void)
pr_err("debugging out of memory - disabling\n");
return NULL;
}
+ __dma_entry_alloc_check_leak();
}
entry = __dma_entry_alloc();
--
2.19.1.dirty
next prev parent reply other threads:[~2018-12-10 14:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-10 14:00 [PATCH v3 0/7] dma-debug cleanup and dynamic allocation Robin Murphy
2018-12-10 14:00 ` [PATCH v3 1/7] dma-debug: Use pr_fmt() Robin Murphy
2018-12-10 14:00 ` [PATCH v3 2/7] dma-debug: Expose nr_total_entries in debugfs Robin Murphy
2018-12-10 14:00 ` [PATCH v3 3/7] dma-debug: Dynamically expand the dma_debug_entry pool Robin Murphy
2018-12-10 14:00 ` Robin Murphy [this message]
2018-12-10 14:00 ` [PATCH v3 5/7] x86/dma/amd-gart: Stop resizing " Robin Murphy
2018-12-10 21:26 ` Thomas Gleixner
2018-12-10 14:00 ` [PATCH v3 6/7] dma/debug: Remove dma_debug_resize_entries() Robin Murphy
2018-12-10 14:00 ` [PATCH v3 7/7] dma-debug: Batch dma_debug_entry allocation Robin Murphy
2018-12-10 15:50 ` [PATCH v3 0/7] dma-debug cleanup and dynamic allocation Qian Cai
2018-12-11 13:43 ` Christoph Hellwig
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