srcu: Explain why callbacks invocations can't run concurrently

If an SRCU barrier is queued while callbacks are running and a new
callbacks invocator for the same sdp were to run concurrently, the
RCU barrier might execute too early. As this requirement is non-obvious,
make sure to keep a record.

Signed-off-by: Frederic Weisbecker <>
Reviewed-by: Joel Fernandes (Google) <>
Signed-off-by: Paul E. McKenney <>
Signed-off-by: Neeraj Upadhyay (AMD) <>
1 file changed