Updating the KCOV documentation to use a load-acquire operation for the first element of the shared memory buffer between kernel-space and user-space.
The load-acquire pairs with the write memory barrier used in kcov_move_area() Signed-off-by: Soham Bagchi <[email protected]> --- Documentation/dev-tools/kcov.rst | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/Documentation/dev-tools/kcov.rst b/Documentation/dev-tools/kcov.rst index 6611434e2dd..46450fb46fe 100644 --- a/Documentation/dev-tools/kcov.rst +++ b/Documentation/dev-tools/kcov.rst @@ -287,6 +287,11 @@ handle instance id. The following program demonstrates using KCOV to collect coverage from both local tasks spawned by the process and the global task that handles USB bus #1: +The user-space code for KCOV should also use an acquire to fetch the count +of coverage entries in the shared buffer. This acquire pairs with the +corresponding write memory barrier (smp_wmb()) on the kernel-side in +kcov_move_area(). + .. code-block:: c /* Same includes and defines as above. */ @@ -361,7 +366,7 @@ local tasks spawned by the process and the global task that handles USB bus #1: */ sleep(2); - n = __atomic_load_n(&cover[0], __ATOMIC_RELAXED); + n = __atomic_load_n(&cover[0], __ATOMIC_ACQUIRE); for (i = 0; i < n; i++) printf("0x%lx\n", cover[i + 1]); if (ioctl(fd, KCOV_DISABLE, 0)) -- 2.34.1
