rcu: Explain why rcu_all_qs() is a stub in preemptible TREE RCU

The cond_resched() function reports an RCU quiescent state only in
non-preemptible TREE RCU implementation.  This commit therefore adds a
comment explaining why cond_resched() does nothing in preemptible kernels.

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

0 files changed, 0 insertions, 0 deletions