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| author | Jason A. Donenfeld | 2016-12-15 06:01:10 +0100 |
|---|---|---|
| committer | Daniel Vetter | 2016-12-16 08:33:40 +0100 |
| commit | 56e3d1cd05cc7b24cfcae8714b0661bf607aaba3 (patch) | |
| tree | 7cbfed2e37d10b0201057cb4fecf75f3f545e84c /include/drm/drm_mm.h | |
| parent | drm: Fix kernel docs for drm_helper_mode_fill_fb_struct() (diff) | |
| download | kernel-qcow2-linux-56e3d1cd05cc7b24cfcae8714b0661bf607aaba3.tar.gz kernel-qcow2-linux-56e3d1cd05cc7b24cfcae8714b0661bf607aaba3.tar.xz kernel-qcow2-linux-56e3d1cd05cc7b24cfcae8714b0661bf607aaba3.zip | |
kref: prefer atomic_inc_not_zero to atomic_add_unless
On most platforms, there exists this ifdef:
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
This makes this patch functionally useless. However, on PPC, there is
actually an explicit definition of atomic_inc_not_zero with its own
assembly that is slightly more optimized than atomic_add_unless. So,
this patch changes kref to use atomic_inc_not_zero instead, for PPC and
any future platforms that might provide an explicit implementation.
This also puts this usage of kref more in line with a verbatim reading
of the examples in Paul McKenney's paper [1] in the section titled "2.4
Atomic Counting With Check and Release Memory Barrier", which uses
atomic_inc_not_zero.
[1] http://open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2167.pdf
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161215050110.3241-1-Jason@zx2c4.com
Diffstat (limited to 'include/drm/drm_mm.h')
0 files changed, 0 insertions, 0 deletions