Commit 22f6b978 authored by Mitchel Humpherys's avatar Mitchel Humpherys Committed by Greg Kroah-Hartman
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staging: ion: WARN when the handle kmap_cnt is going to wrap around 



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: default avatarMitchel Humpherys <mitchelh@codeaurora.org>
Acked-by: default avatarColin Cross <ccross@android.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7949f30a

drivers/staging/android/ion/ion.c

+4 −0
Original line number Diff line number Diff line
@@ -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);