We can always get EINTR for read; /dev/urandom is no exception.
Rearrange the order of tests for likelihood; allow degenerate buflen==0
case to perform a no-op zero-length read. This means that the normal
success path is a straight line with a single test for success.
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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