diff options
authorMinchan Kim <minchan@kernel.org>2018-05-07 23:15:37 +0900
committerMartijn Coenen <maco@android.com>2018-07-17 11:14:22 +0200
commit2cafd5b9fa61bfd77391f66116e629a872f6b025 (patch)
parente1b1a8be1d974793876bd9ce7a03d86ee4333cc7 (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
2 files changed, 6 insertions, 4 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 2ed6f33d5254..129568e815cb 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4898,7 +4898,9 @@ 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 6c646fdd1cc4..bec6c0a90429 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -219,7 +219,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
mm = alloc->vma_vm_mm;
if (mm) {
- down_write(&mm->mmap_sem);
+ down_read(&mm->mmap_sem);
vma = alloc->vma;
@@ -288,7 +288,7 @@ 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);
return 0;
@@ -321,7 +321,7 @@ err_page_ptr_cleared:
if (mm) {
- up_write(&mm->mmap_sem);
+ up_read(&mm->mmap_sem);
return vma ? -ENOMEM : -ESRCH;