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 /drivers | |
| 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 'drivers')
| -rw-r--r-- | drivers/android/binder.c | 4 | ||||
| -rw-r--r-- | drivers/android/binder_alloc.c | 6 |
2 files changed, 6 insertions, 4 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c index f5a4f2c66..83880dc13 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -4841,7 +4841,9 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma) failure_string = "bad vm_flags"; goto err_bad_arg; } - vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE; + vma->vm_flags |= VM_DONTCOPY | VM_MIXEDMAP; + vma->vm_flags &= ~VM_MAYWRITE; + vma->vm_ops = &binder_vm_ops; vma->vm_private_data = proc; diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index cf6daeb27..a7c2ce54e 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -199,7 +199,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, mm = get_task_mm(alloc->tsk); if (mm) { - down_write(&mm->mmap_sem); + down_read(&mm->mmap_sem); vma = alloc->vma; if (vma && mm != alloc->vma_vm_mm) { pr_err("%d: vma mm and task mm mismatch\n", @@ -249,7 +249,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, /* vm_insert_page does not seem to increment the refcount */ } if (mm) { - up_write(&mm->mmap_sem); + up_read(&mm->mmap_sem); mmput(mm); } return 0; @@ -271,7 +271,7 @@ err_alloc_page_failed: } err_no_vma: if (mm) { - up_write(&mm->mmap_sem); + up_read(&mm->mmap_sem); mmput(mm); } return vma ? -ENOMEM : -ESRCH; |