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staging: ion: WARN when the handle kmap_cnt is going to wrap around

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There are certain client bugs (double unmap, for example) that can cause
the handle->kmap_cnt (an unsigned int) to wrap around from zero. This
causes problems when the handle is destroyed because we have:

        while (handle->kmap_cnt)
                ion_handle_kmap_put(handle);

which takes a long time to complete when kmap_cnt starts at ~0 and can
result in a watchdog timeout.

WARN and bail when kmap_cnt is about to wrap around from zero.

Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Acked-by: Colin Cross <ccross@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mitchel Humpherys 2014-05-23 13:01:22 -07:00 committed by Greg Kroah-Hartman
parent 7949f30a36
commit 22f6b9789a
1 changed files with 4 additions and 0 deletions
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4
drivers/staging/android/ion/ion.c
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@ -627,6 +627,10 @@ static void ion_handle_kmap_put(struct ion_handle *handle)
{
struct ion_buffer *buffer = handle->buffer;
if (!handle->kmap_cnt) {
WARN(1, "%s: Double unmap detected! bailing...\n", __func__);
return;
}
handle->kmap_cnt--;
if (!handle->kmap_cnt)
ion_buffer_kmap_put(buffer);