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Subject[PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page()
Date
The use of kmap_atomic() is being deprecated in favor of kmap_local_page()
where it is feasible. Each call of kmap_atomic() in the kernel creates
a non-preemptible section and disable pagefaults. This could be a source
of unwanted latency, so it should be only used if it is absolutely
required, otherwise kmap_local_page() should be preferred.

With kmap_local_page(), the mapping is per thread, CPU local and not
globally visible. Furthermore, the mapping can be acquired from any context
(including interrupts).

Therefore, use kmap_local_page() / kunmap_local() in place of
kmap_atomic() / kunmap_atomic().

Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---
drivers/android/binder_alloc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 0875c463c002..058595cc7ff0 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1250,17 +1250,17 @@ static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
page = binder_alloc_get_page(alloc, buffer,
buffer_offset, &pgoff);
size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
- base_ptr = kmap_atomic(page);
+ base_ptr = kmap_local_page(page);
tmpptr = base_ptr + pgoff;
if (to_buffer)
memcpy(tmpptr, ptr, size);
else
memcpy(ptr, tmpptr, size);
/*
- * kunmap_atomic() takes care of flushing the cache
+ * kunmap_local() takes care of flushing the cache
* if this device has VIVT cache arch
*/
- kunmap_atomic(base_ptr);
+ kunmap_local(base_ptr);
bytes -= size;
pgoff = 0;
ptr = ptr + size;
--
2.34.1
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