diff options
| author | Minchan Kim <minchan@kernel.org> | 2018-05-07 23:15:37 +0900 |
|---|---|---|
| committer | Moyster <oysterized@gmail.com> | 2018-11-29 10:59:46 +0100 |
| commit | 3702e61005b6491b814dc539300d4d413831086e (patch) | |
| tree | 9fb8e4728b340bffdfd4c14a5284bc6576f89e52 /kernel/debug | |
| parent | 94e780c6f1e8779b4aba2d50523bc4b0d95c9317 (diff) | |
UPSTREAM: ANDROID: binder: change down_write to down_read
binder_update_page_range needs down_write of mmap_sem because
vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless
it is set. However, when I profile binder working, it seems
every binder buffers should be mapped in advance by binder_mmap.
It means we could set VM_MIXEDMAP in binder_mmap time which is
already hold a mmap_sem as down_write so binder_update_page_range
doesn't need to hold a mmap_sem as down_write.
Please use proper API down_read. It would help mmap_sem contention
problem as well as fixing down_write abuse.
Ganesh Mahendran tested app launching and binder throughput test
and he said he couldn't find any problem and I did binder latency
test per Greg KH request(Thanks Martijn to teach me how I can do)
I cannot find any problem, too.
Cc: Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Todd Kjos <tkjos@google.com>
Reviewed-by: Martijn Coenen <maco@android.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 720c241924046aff83f5f2323232f34a30a4c281)
Change-Id: I8358ceaaab4030f7122c95308dcad59557cad411
Diffstat (limited to 'kernel/debug')
0 files changed, 0 insertions, 0 deletions