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| author | Minchan Kim <minchan@kernel.org> | 2019-02-18 17:11:45 +0900 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-02-19 14:50:11 +0100 |
| commit | 3013bf62b67aef921bc2e9ba10e639a022002d02 (patch) | |
| tree | 783ad1e60175ec150ea953276af0f8ab6e8fab49 | |
| parent | 7c11df42d0c7bf5b3dd743a21b4872e7b26ca2a2 (diff) | |
| download | linux-3013bf62b67aef921bc2e9ba10e639a022002d02.tar.gz linux-3013bf62b67aef921bc2e9ba10e639a022002d02.tar.bz2 linux-3013bf62b67aef921bc2e9ba10e639a022002d02.zip | |
binder: reduce mmap_sem write-side lock
binder has used write-side mmap_sem semaphore to release memory
mapped at address space of the process. However, right lock to
release pages is down_read, not down_write because page table lock
already protects the race for parallel freeing.
Please do not use mmap_sem write-side lock which is well known
contented lock.
Cc: Todd Kjos <tkjos@google.com>
Cc: Martijn Coenen <maco@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/android/binder_alloc.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index 000dd4d145ba..6389467670a0 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -932,7 +932,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item, if (!mmget_not_zero(alloc->vma_vm_mm)) goto err_mmget; mm = alloc->vma_vm_mm; - if (!down_write_trylock(&mm->mmap_sem)) + if (!down_read_trylock(&mm->mmap_sem)) goto err_down_write_mmap_sem_failed; } @@ -946,7 +946,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item, trace_binder_unmap_user_end(alloc, index); - up_write(&mm->mmap_sem); + up_read(&mm->mmap_sem); mmput(mm); } |