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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> |
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| .. | ||
| binder_alloc_selftest.c | ||
| binder_alloc.c | ||
| binder_alloc.h | ||
| binder_trace.h | ||
| binder.c | ||
| Kconfig | ||
| Makefile | ||