AcoSail/kernel_optimize_test
8
0
Fork 0
forked from luck/tmp_suning_uos_patched
Code Pull Requests Activity

dma-debug: Make leak-like behaviour apparent

Browse Source 
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>
This commit is contained in:
Robin Murphy 2018-12-10 14:00:30 +00:00 committed by Christoph Hellwig
parent 2b9d9ac02b
commit ceb51173b2
2 changed files with 18 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/DMA-API.txt
View File

@ -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.
::

13
kernel/dma/debug.c
View File

@ -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();