| Message ID | 20230510-dt-resv-bottom-up-v2-2-aeb2afc8ac25@gerhold.net (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | of: reserved_mem: Improve range allocations | expand |
On Wed, 14 Jun 2023 21:20:43 +0200, Stephan Gerhold wrote: > sort() in Linux is based on heapsort which is not a stable sort > algorithm - equal elements are being reordered. For reserved memory in > the device tree this happens mainly for dynamic allocations: They do not > have an address to sort with, so they are reordered somewhat randomly > when adding/removing other unrelated reserved memory nodes. > > Functionally this is not a big problem, but it's confusing during > development when all the addresses change after adding unrelated > reserved memory nodes. > > Make the order stable by sorting dynamic allocations according to > the node order in the device tree. Static allocations are not affected > by this because they are still sorted by their (fixed) address. > > Signed-off-by: Stephan Gerhold <stephan@gerhold.net> > --- > drivers/of/of_reserved_mem.c | 5 +++++ > 1 file changed, 5 insertions(+) > Applied, thanks!
diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c index 7f892c3dcc63..7ec94cfcbddb 100644 --- a/drivers/of/of_reserved_mem.c +++ b/drivers/of/of_reserved_mem.c @@ -268,6 +268,11 @@ static int __init __rmem_cmp(const void *a, const void *b) if (ra->size > rb->size) return 1; + if (ra->fdt_node < rb->fdt_node) + return -1; + if (ra->fdt_node > rb->fdt_node) + return 1; + return 0; }
sort() in Linux is based on heapsort which is not a stable sort algorithm - equal elements are being reordered. For reserved memory in the device tree this happens mainly for dynamic allocations: They do not have an address to sort with, so they are reordered somewhat randomly when adding/removing other unrelated reserved memory nodes. Functionally this is not a big problem, but it's confusing during development when all the addresses change after adding unrelated reserved memory nodes. Make the order stable by sorting dynamic allocations according to the node order in the device tree. Static allocations are not affected by this because they are still sorted by their (fixed) address. Signed-off-by: Stephan Gerhold <stephan@gerhold.net> --- drivers/of/of_reserved_mem.c | 5 +++++ 1 file changed, 5 insertions(+)